diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6aae7fce..4f9a7485 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,66 @@
+## 1.22.5
+
+### JavaScript API
+
+* Improve performance for logic-heavy stylesheets.
+
+## 1.22.4
+
+* Fix a bug where at-rules imported from within a style rule would appear within
+  that style rule rather than at the root of the document.
+
+## 1.22.3
+
+* **Potentially breaking bug fix:** The argument name for the `saturate()`
+  function is now `$amount`, to match the name in LibSass and originally in Ruby
+  Sass.
+
+* **Potentially breaking bug fix:** The `invert()` function now properly returns
+  `#808080` when passed `$weight: 50%`. This matches the behavior in LibSass and
+  originally in Ruby Sass, as well as being consistent with other nearby values
+  of `$weight`.
+
+* **Potentially breaking bug fix:** The `invert()` function now throws an error
+  if it's used [as a plain CSS function][plain-CSS invert] *and* the Sass-only
+  `$weight` parameter is passed. This never did anything useful, so it's
+  considered a bug fix rather than a full breaking change.
+  
+  [plain-CSS invert]: https://developer.mozilla.org/en-US/docs/Web/CSS/filter-function/invert
+
+* **Potentially breaking bug fix**: The `str-insert()` function now properly
+  inserts at the end of the string if the `$index` is `-1`. This matches the
+  behavior in LibSass and originally in Ruby Sass.
+
+* **Potentially breaking bug fix**: An empty map returned by `map-remove()` is
+  now treated as identical to the literal value `()`, rather than being treated
+  as though it had a comma separator. This matches the original behavior in Ruby
+  Sass.
+
+* The `adjust-color()` function no longer throws an error when a large `$alpha`
+  value is combined with HSL adjustments.
+
+* The `alpha()` function now produces clearer error messages when the wrong
+  number of arguments are passed.
+
+* Fix a bug where the `str-slice()` function could produce invalid output when
+  passed a string that contains characters that aren't represented as a single
+  byte in UTF-16.
+
+* Improve the error message for an unknown separator name passed to the `join()`
+  or `append()` functions.
+
+* The `zip()` function no longer deadlocks if passed no arguments.
+
+* The `map-remove()` function can now take a `$key` named argument. This matches
+  the signature in LibSass and originally in Ruby Sass.
+
+## 1.22.2
+
+### JavaScript API
+
+* Avoid re-assigning the `require()` function to make the code statically
+  analyzable by Webpack.
+
 ## 1.22.1
 
 ### JavaScript API
@@ -27,11 +90,6 @@
 * Add a top-level `warn()` function for custom functions and importers to print
   warning messages.
 
-### JavaScript API
-
-* Avoid re-assigning the `require()` function to make the code statically
-  analyzable by Webpack.
-
 ## 1.20.3
 
 * No user-visible changes.
diff --git a/lib/src/functions/color.dart b/lib/src/functions/color.dart
index 3ea3292e..7cb7a05f 100644
--- a/lib/src/functions/color.dart
+++ b/lib/src/functions/color.dart
@@ -47,16 +47,20 @@ final global = UnmodifiableListView([
     }
   }),
 
-  BuiltInCallable("invert", r"$color, $weight: 50%", (arguments) {
+  BuiltInCallable("invert", r"$color, $weight: 100%", (arguments) {
+    var weight = arguments[1].assertNumber("weight");
     if (arguments[0] is SassNumber) {
+      if (weight.value != 100 || !weight.hasUnit("%")) {
+        throw "Only one argument may be passed to the plain-CSS invert() "
+            "function.";
+      }
+
       return _functionString("invert", arguments.take(1));
     }
 
     var color = arguments[0].assertColor("color");
-    var weight = arguments[1].assertNumber("weight");
     var inverse = color.changeRgb(
         red: 255 - color.red, green: 255 - color.green, blue: 255 - color.blue);
-    if (weight.value == 50) return inverse;
 
     return _mixColors(inverse, color, weight);
   }),
@@ -130,8 +134,8 @@ final global = UnmodifiableListView([
   }),
 
   BuiltInCallable.overloaded("saturate", {
-    r"$number": (arguments) {
-      var number = arguments[0].assertNumber("number");
+    r"$amount": (arguments) {
+      var number = arguments[0].assertNumber("amount");
       return SassString("saturate(${number.toCssString()})", quotes: false);
     },
     r"$color, $amount": (arguments) {
@@ -171,17 +175,23 @@ final global = UnmodifiableListView([
       return SassNumber(color.alpha);
     },
     r"$args...": (arguments) {
-      if (arguments[0].asList.every((argument) =>
-          argument is SassString &&
-          !argument.hasQuotes &&
-          argument.text.contains(_microsoftFilterStart))) {
+      var argList = arguments[0].asList;
+      if (argList.isNotEmpty &&
+          argList.every((argument) =>
+              argument is SassString &&
+              !argument.hasQuotes &&
+              argument.text.contains(_microsoftFilterStart))) {
         // Suport the proprietary Microsoft alpha() function.
         return _functionString("alpha", arguments);
       }
 
-      assert(arguments.length != 1);
-      throw SassScriptException(
-          "Only 1 argument allowed, but ${arguments.length} were passed.");
+      assert(argList.length != 1);
+      if (argList.isEmpty) {
+        throw SassScriptException("Missing argument \$color.");
+      } else {
+        throw SassScriptException(
+            "Only 1 argument allowed, but ${argList.length} were passed.");
+      }
     }
   }),
 
@@ -206,8 +216,14 @@ final module = BuiltInModule("color", functions: [
   // ### RGB
   _red, _green, _blue, _mix,
 
-  BuiltInCallable("invert", r"$color, $weight: 50%", (arguments) {
+  BuiltInCallable("invert", r"$color, $weight: 100%", (arguments) {
+    var weight = arguments[1].assertNumber("weight");
     if (arguments[0] is SassNumber) {
+      if (weight.value != 100 || !weight.hasUnit("%")) {
+        throw "Only one argument may be passed to the plain-CSS invert() "
+            "function.";
+      }
+
       var result = _functionString("invert", arguments.take(1));
       warn("Passing a number to color.invert() is deprecated.\n"
           "\n"
@@ -216,10 +232,8 @@ final module = BuiltInModule("color", functions: [
     }
 
     var color = arguments[0].assertColor("color");
-    var weight = arguments[1].assertNumber("weight");
     var inverse = color.changeRgb(
         red: 255 - color.red, green: 255 - color.green, blue: 255 - color.blue);
-    if (weight.value == 50) return inverse;
 
     return _mixColors(inverse, color, weight);
   }),
@@ -400,7 +414,7 @@ final _adjust = BuiltInCallable("adjust", r"$color, $kwargs...", (arguments) {
         hue: color.hue + (hue ?? 0),
         saturation: (color.saturation + (saturation ?? 0)).clamp(0, 100),
         lightness: (color.lightness + (lightness ?? 0)).clamp(0, 100),
-        alpha: color.alpha + (alpha ?? 0));
+        alpha: (color.alpha + (alpha ?? 0)).clamp(0, 1));
   } else if (alpha != null) {
     return color.changeAlpha((color.alpha + (alpha ?? 0)).clamp(0, 1));
   } else {
diff --git a/lib/src/functions/list.dart b/lib/src/functions/list.dart
index a082705e..7f460b62 100644
--- a/lib/src/functions/list.dart
+++ b/lib/src/functions/list.dart
@@ -63,7 +63,7 @@ final _join = BuiltInCallable(
     separator = ListSeparator.comma;
   } else {
     throw SassScriptException(
-        '\$$separator: Must be "space", "comma", or "auto".');
+        '\$separator: Must be "space", "comma", or "auto".');
   }
 
   var bracketed = bracketedParam is SassString && bracketedParam.text == 'auto'
@@ -91,7 +91,7 @@ final _append =
     separator = ListSeparator.comma;
   } else {
     throw SassScriptException(
-        '\$$separator: Must be "space", "comma", or "auto".');
+        '\$separator: Must be "space", "comma", or "auto".');
   }
 
   var newList = [...list.asList, value];
@@ -100,6 +100,10 @@ final _append =
 
 final _zip = BuiltInCallable("zip", r"$lists...", (arguments) {
   var lists = arguments[0].asList.map((list) => list.asList).toList();
+  if (lists.isEmpty) {
+    return const SassList.empty(separator: ListSeparator.comma);
+  }
+
   var i = 0;
   var results = <SassList>[];
   while (lists.every((list) => i != list.length)) {
diff --git a/lib/src/functions/map.dart b/lib/src/functions/map.dart
index d44c53ad..9ca6a302 100644
--- a/lib/src/functions/map.dart
+++ b/lib/src/functions/map.dart
@@ -36,14 +36,23 @@ final _merge = BuiltInCallable("merge", r"$map1, $map2", (arguments) {
   return SassMap({...map1.contents, ...map2.contents});
 });
 
-final _remove = BuiltInCallable("remove", r"$map, $keys...", (arguments) {
-  var map = arguments[0].assertMap("map");
-  var keys = arguments[1];
-  var mutableMap = Map.of(map.contents);
-  for (var key in keys.asList) {
-    mutableMap.remove(key);
+final _remove = BuiltInCallable.overloaded("remove", {
+  // Because the signature below has an explicit `$key` argument, it doesn't
+  // allow zero keys to be passed. We want to allow that case, so we add an
+  // explicit overload for it.
+  r"$map": (arguments) => arguments[0].assertMap("map"),
+
+  // The first argument has special handling so that the $key parameter can be
+  // passed by name.
+  r"$map, $key, $keys...": (arguments) {
+    var map = arguments[0].assertMap("map");
+    var keys = [arguments[1], ...arguments[2].asList];
+    var mutableMap = Map.of(map.contents);
+    for (var key in keys) {
+      mutableMap.remove(key);
+    }
+    return SassMap(mutableMap);
   }
-  return SassMap(mutableMap);
 });
 
 final _keys = BuiltInCallable(
diff --git a/lib/src/functions/string.dart b/lib/src/functions/string.dart
index 4ff096b3..03b7728d 100644
--- a/lib/src/functions/string.dart
+++ b/lib/src/functions/string.dart
@@ -64,10 +64,13 @@ final _insert =
   // the `$insert` string is at `$index` in the result, which means that we
   // want to insert before `$index` if it's positive and after if it's
   // negative.
-  if (indexInt < 0) indexInt++;
+  if (indexInt < 0) {
+    // +1 because negative indexes start counting from -1 rather than 0, and
+    // another +1 because we want to insert *after* that index.
+    indexInt = string.sassLength + indexInt + 2;
+  }
 
   var codepointIndex = _codepointForIndex(indexInt, string.sassLength);
-
   var codeUnitIndex =
       codepointIndexToCodeUnitIndex(string.text, codepointIndex);
   return SassString(
@@ -113,7 +116,7 @@ final _slice =
   return SassString(
       string.text.substring(
           codepointIndexToCodeUnitIndex(string.text, startCodepoint),
-          codepointIndexToCodeUnitIndex(string.text, endCodepoint) + 1),
+          codepointIndexToCodeUnitIndex(string.text, endCodepoint + 1)),
       quotes: string.hasQuotes);
 });
 
diff --git a/lib/src/io/vm.dart b/lib/src/io/vm.dart
index c1399167..aa5eaf06 100644
--- a/lib/src/io/vm.dart
+++ b/lib/src/io/vm.dart
@@ -74,7 +74,7 @@ void ensureDir(String path) => io.Directory(path).createSync(recursive: true);
 Iterable<String> listDir(String path, {bool recursive = false}) =>
     io.Directory(path)
         .listSync(recursive: recursive)
-        .where((entity) => entity is io.File)
+        .whereType<io.File>()
         .map((entity) => entity.path);
 
 DateTime modificationTime(String path) {
diff --git a/lib/src/parse/scss.dart b/lib/src/parse/scss.dart
index 37cbd7fe..43903328 100644
--- a/lib/src/parse/scss.dart
+++ b/lib/src/parse/scss.dart
@@ -153,7 +153,7 @@ class ScssParser extends StylesheetParser {
     } while (scanner.scan("//"));
 
     if (plainCss) {
-      error("Silent comments arne't allowed in plain CSS.",
+      error("Silent comments aren't allowed in plain CSS.",
           scanner.spanFrom(start));
     }
 
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index aecde2f6..5bf5e60a 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -306,7 +306,11 @@ bool startsWithIgnoreSeparator(String string, String prefix) {
 /// If [source] is passed, copies it into the map.
 Map<String, V> normalizedMap<V>([Map<String, V> source]) {
   var map = LinkedHashMap<String, V>(
-      equals: equalsIgnoreSeparator, hashCode: hashCodeIgnoreSeparator);
+      // Explicitly set this because the default implementation involves a type
+      // check, which is very expensive in dart2js.
+      isValidKey: (_) => true,
+      equals: equalsIgnoreSeparator,
+      hashCode: hashCodeIgnoreSeparator);
   if (source != null) map.addAll(source);
   return map;
 }
@@ -316,7 +320,11 @@ Map<String, V> normalizedMap<V>([Map<String, V> source]) {
 /// If [source] is passed, copies it into the set.
 Set<String> normalizedSet([Iterable<String> source]) {
   var set = LinkedHashSet(
-      equals: equalsIgnoreSeparator, hashCode: hashCodeIgnoreSeparator);
+      // Explicitly set this because the default implementation involves a type
+      // check, which is very expensive in dart2js.
+      isValidKey: (_) => true,
+      equals: equalsIgnoreSeparator,
+      hashCode: hashCodeIgnoreSeparator);
   if (source != null) set.addAll(source);
   return set;
 }
diff --git a/lib/src/value/map.dart b/lib/src/value/map.dart
index f33128af..22d26c13 100644
--- a/lib/src/value/map.dart
+++ b/lib/src/value/map.dart
@@ -10,7 +10,8 @@ import 'external/value.dart' as ext;
 class SassMap extends Value implements ext.SassMap {
   final Map<Value, Value> contents;
 
-  ListSeparator get separator => ListSeparator.comma;
+  ListSeparator get separator =>
+      contents.isEmpty ? ListSeparator.undecided : ListSeparator.comma;
 
   List<Value> get asList {
     var result = <Value>[];
diff --git a/lib/src/visitor/async_evaluate.dart b/lib/src/visitor/async_evaluate.dart
index b3388d0d..172db3e2 100644
--- a/lib/src/visitor/async_evaluate.dart
+++ b/lib/src/visitor/async_evaluate.dart
@@ -2133,15 +2133,19 @@ class _EvaluateVisitor
       {bool trackSpans}) async {
     trackSpans ??= _sourceMap;
 
-    var positional = (await mapAsync(arguments.positional,
-            (Expression expression) => expression.accept(this)))
-        .toList();
+    var positional = [
+      for (var expression in arguments.positional) await expression.accept(this)
+    ];
     var named = await normalizedMapMapAsync<String, Expression, Value>(
         arguments.named,
         value: (_, expression) => expression.accept(this));
 
-    var positionalNodes =
-        trackSpans ? arguments.positional.map(_expressionNode).toList() : null;
+    var positionalNodes = trackSpans
+        ? [
+            for (var expression in arguments.positional)
+              _expressionNode(expression)
+          ]
+        : null;
     var namedNodes = trackSpans
         ? mapMap<String, Expression, String, AstNode>(arguments.named,
             value: (_, expression) => _expressionNode(expression))
@@ -2796,7 +2800,10 @@ class _ImportedCssVisitor implements ModifiableCssVisitor<void> {
 
   _ImportedCssVisitor(this._visitor);
 
-  void visitCssAtRule(ModifiableCssAtRule node) => _visitor._addChild(node);
+  void visitCssAtRule(ModifiableCssAtRule node) {
+    _visitor._addChild(node,
+        through: node.isChildless ? null : (node) => node is CssStyleRule);
+  }
 
   void visitCssComment(ModifiableCssComment node) => _visitor._addChild(node);
 
diff --git a/lib/src/visitor/evaluate.dart b/lib/src/visitor/evaluate.dart
index 7352ab26..475ea380 100644
--- a/lib/src/visitor/evaluate.dart
+++ b/lib/src/visitor/evaluate.dart
@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_evaluate.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: 2dc9fdf171d8c876f24994eb0e106328154497c4
+// Checksum: f6ac9bc98278f8019357f5d6d56d46f46636f4bc
 //
 // ignore_for_file: unused_import
 
@@ -2119,14 +2119,18 @@ class _EvaluateVisitor
       {bool trackSpans}) {
     trackSpans ??= _sourceMap;
 
-    var positional = arguments.positional
-        .map((Expression expression) => expression.accept(this))
-        .toList();
+    var positional = [
+      for (var expression in arguments.positional) expression.accept(this)
+    ];
     var named = normalizedMapMap<String, Expression, Value>(arguments.named,
         value: (_, expression) => expression.accept(this));
 
-    var positionalNodes =
-        trackSpans ? arguments.positional.map(_expressionNode).toList() : null;
+    var positionalNodes = trackSpans
+        ? [
+            for (var expression in arguments.positional)
+              _expressionNode(expression)
+          ]
+        : null;
     var namedNodes = trackSpans
         ? mapMap<String, Expression, String, AstNode>(arguments.named,
             value: (_, expression) => _expressionNode(expression))
@@ -2760,7 +2764,10 @@ class _ImportedCssVisitor implements ModifiableCssVisitor<void> {
 
   _ImportedCssVisitor(this._visitor);
 
-  void visitCssAtRule(ModifiableCssAtRule node) => _visitor._addChild(node);
+  void visitCssAtRule(ModifiableCssAtRule node) {
+    _visitor._addChild(node,
+        through: node.isChildless ? null : (node) => node is CssStyleRule);
+  }
 
   void visitCssComment(ModifiableCssComment node) => _visitor._addChild(node);
 
diff --git a/perf.md b/perf.md
index d0ec2819..96f7f703 100644
--- a/perf.md
+++ b/perf.md
@@ -3,8 +3,8 @@ the benefit Dart Sass could provide relative to other implementations.
 
 This was tested against:
 
-* libsass 8d220b74 and sassc 3f84e23 compiled with g++ (Debian 7.3.0-18) 7.3.0.
-* Dart Sass 2868ab3 on Dart 2.3.0 and Node v11.14.0.
+* libsass 0f3d6ad1 and sassc 4674821 compiled with g++ (Debian 7.3.0-18) 7.3.0.
+* Dart Sass 50a45a7 on Dart 2.4.0 and Node v12.0.0.
 * Ruby Sass 8d1edc76 on ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-linux].
 
 on Debian x64 with Intel Xeon E5-1650 v3 @ 3.50GHz. The Dart Sass
@@ -20,148 +20,150 @@ I ran five instances of each configuration and recorded the fastest time.
 
 Running on a file containing 4 instances of `.foo {a: b}`:
 
-* sassc: 0.004s
-* Dart Sass from a script snapshot: 0.188s
-* Dart Sass native executable: 0.014s
-* Dart Sass on Node.js: 0.169s
-* Ruby Sass with a hot cache: 0.151s
+* sassc: 0.005s
+* Dart Sass from a script snapshot: 0.216s
+* Dart Sass native executable: 0.018s
+* Dart Sass on Node.js: 0.209s
+* Ruby Sass with a hot cache: 0.148s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 3.5x slower than libsass
-* 12.1x faster than Dart Sass on Node
-* 10.8x faster than Ruby Sass
+* 3.6x slower than libsass
+* 11.6x faster than Dart Sass on Node
+* 8.2x faster than Ruby Sass
 
 ## Large Plain CSS
 
 Running on a file containing 2^17 instances of `.foo {a: b}`:
 
-* sassc: 1.909s
-* Dart Sass from a script snapshot: 1.586s
-* Dart Sass native executable: 1.438s
-* Dart Sass on Node.js: 3.028s
-* Ruby Sass with a hot cache: 10.772s
+* sassc: 1.705s
+* Dart Sass from a script snapshot: 1.550s
+* Dart Sass native executable: 1.518s
+* Dart Sass on Node.js: 2.765s
+* Ruby Sass with a hot cache: 10.965s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.3x faster than libsass
-* 2.1x faster than Dart Sass on Node
-* 7.5x faster than Ruby Sass
+* 1.1x faster than libsass
+* 1.8x faster than Dart Sass on Node
+* 7.2x faster than Ruby Sass
 
 ## Preceding Sparse `@extend`
 
 Running on a file containing `.x {@extend .y}`, 2^17 instances of `.foo {a: b}`, and then `.y {a: b}`:
 
-* sassc: 2.007s
-* Dart Sass from a script snapshot: 1.617s
-* Dart Sass native executable: 1.457s
-* Dart Sass on Node.js: 3.072s
-* Ruby Sass with a hot cache: 16.456s
+* sassc: 1.712s
+* Dart Sass from a script snapshot: 1.613s
+* Dart Sass native executable: 1.582s
+* Dart Sass on Node.js: 2.739s
+* Ruby Sass with a hot cache: 16.472s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.4x faster than libsass
-* 2.1x faster than Dart Sass on Node
-* 11.3x faster than Ruby Sass
+* 1.1x faster than libsass
+* 1.7x faster than Dart Sass on Node
+* 10.4x faster than Ruby Sass
 
 ## Following Sparse `@extend`
 
 Running on a file containing `.y {a: b}`, 2^17 instances of `.foo {a: b}`, and then `.x {@extend .y}`:
 
-* sassc: 1.934s
-* Dart Sass from a script snapshot: 1.594s
-* Dart Sass native executable: 1.433s
-* Dart Sass on Node.js: 3.099s
-* Ruby Sass with a hot cache: 16.497s
+* sassc: 1.701s
+* Dart Sass from a script snapshot: 1.568s
+* Dart Sass native executable: 1.543s
+* Dart Sass on Node.js: 2.821s
+* Ruby Sass with a hot cache: 16.469s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.3x faster than libsass
-* 2.2x faster than Dart Sass on Node
-* 11.5x faster than Ruby Sass
+* 1.1x faster than libsass
+* 1.8x faster than Dart Sass on Node
+* 10.7x faster than Ruby Sass
 
 ## Preceding Dense `@extend`
 
 Running on a file containing `.bar {@extend .foo}` followed by 2^17 instances of `.foo {a: b}`:
 
-* sassc: 2.033s
-* Dart Sass from a script snapshot: 2.380s
-* Dart Sass native executable: 2.398s
-* Dart Sass on Node.js: 6.523s
-* Ruby Sass with a hot cache: 29.717s
+* sassc: 2.260s
+* Dart Sass from a script snapshot: 2.405s
+* Dart Sass native executable: 2.526s
+* Dart Sass on Node.js: 5.612s
+* Ruby Sass with a hot cache: 28.690s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.2x slower than libsass
-* 2.7x faster than Dart Sass on Node
-* 12.4x faster than Ruby Sass
+* 1.1x slower than libsass
+* 2.2x faster than Dart Sass on Node
+* 11.4x faster than Ruby Sass
 
 ## Following Dense `@extend`
 
 Running on a file containing 2^17 instances of `.foo {a: b}` followed by `.bar {@extend .foo}`:
 
-* sassc: 2.065s
-* Dart Sass from a script snapshot: 2.312s
-* Dart Sass native executable: 2.256s
-* Dart Sass on Node.js: 6.760s
-* Ruby Sass with a hot cache: 28.755s
+* sassc: 2.289s
+* Dart Sass from a script snapshot: 2.396s
+* Dart Sass native executable: 2.457s
+* Dart Sass on Node.js: 6.319s
+* Ruby Sass with a hot cache: 28.708s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 1.1x slower than libsass
-* 3.0x faster than Dart Sass on Node
-* 12.7x faster than Ruby Sass
+* 2.6x faster than Dart Sass on Node
+* 11.7x faster than Ruby Sass
 
 ## Bootstrap
 
 Running on a file containing 16 instances of importing the Bootstrap framework:
 
-* sassc: 0.898s
-* Dart Sass from a script snapshot: 1.550s
-* Dart Sass native executable: 0.907s
-* Dart Sass on Node.js: 3.559s
-* Ruby Sass with a hot cache: 12.649s
+* sassc: 0.767s
+* Dart Sass from a script snapshot: 1.534s
+* Dart Sass native executable: 0.955s
+* Dart Sass on Node.js: 3.156s
+* Ruby Sass with a hot cache: 12.521s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* identical to libsass
-* 3.9x faster than Dart Sass on Node
-* 13.9x faster than Ruby Sass
+* 1.2x slower than libsass
+* 3.3x faster than Dart Sass on Node
+* 13.1x faster than Ruby Sass
 
 ## a11ycolor
 
 Running on a file containing test cases for a computation-intensive color-processing library:
 
-* sassc: 0.332s
-* Dart Sass from a script snapshot: 0.726s
-* Dart Sass native executable: 0.564s
-* Dart Sass on Node.js: 2.027s
-* Ruby Sass with a hot cache: 5.020s
+* sassc: 0.248s
+* Dart Sass from a script snapshot: 0.736s
+* Dart Sass native executable: 0.565s
+* Dart Sass on Node.js: 1.043s
+* Ruby Sass with a hot cache: 5.091s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.7x slower than libsass
-* 3.6x faster than Dart Sass on Node
-* 8.9x faster than Ruby Sass
+* 2.3x slower than libsass
+* 1.8x faster than Dart Sass on Node
+* 9.0x faster than Ruby Sass
 
 ## Susy
 
 Running on a file containing test cases for the computation-intensive Susy grid framework:
 
-* sassc: 0.290s
-* Dart Sass from a script snapshot: 0.649s
-* Dart Sass native executable: 0.225s
-* Dart Sass on Node.js: 1.293s
-* Ruby Sass with a hot cache: 1.506s
+* sassc: 0.248s
+* Dart Sass from a script snapshot: 0.673s
+* Dart Sass native executable: 0.237s
+* Dart Sass on Node.js: 0.990s
+* Ruby Sass with a hot cache: 1.527s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.3x faster than libsass
-* 5.7x faster than Dart Sass on Node
-* 6.7x faster than Ruby Sass
+* identical to libsass
+* 4.2x faster than Dart Sass on Node
+* 6.4x faster than Ruby Sass
 
 # Prior Measurements
 
+* [1.22.4](https://github.com/sass/dart-sass/blob/a7172a2b1dd48b339e5d57159ed364ffb9f5812e/perf.md).
+* [1.20.2](https://github.com/sass/dart-sass/blob/4b7699291c9f69533d25980d23b0647266b665f2/perf.md).
 * [1.13.4](https://github.com/sass/dart-sass/blob/b6ccc91a138e75420227ff79381c5f70e60254f1/perf.md).
 * [1.6.0](https://github.com/sass/dart-sass/blob/048cbe197a77e1cf4b837a40a5acb737e949fd5c/perf.md).
 * [1.0.0-alpha.8](https://github.com/sass/dart-sass/blob/be44245a849f2bb18b5ca1fc74f3043a36da17f0/perf.md).
diff --git a/pubspec.yaml b/pubspec.yaml
index 690eaebb..a4b51b53 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sass
-version: 1.22.1
+version: 1.22.5
 description: A Sass implementation in Dart.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/sass/dart-sass
diff --git a/test/dart_api/value/map_test.dart b/test/dart_api/value/map_test.dart
index d6391674..71fe0e78 100644
--- a/test/dart_api/value/map_test.dart
+++ b/test/dart_api/value/map_test.dart
@@ -15,7 +15,7 @@ main() {
     SassMap value;
     setUp(() => value = parseValue("(a: b, c: d)") as SassMap);
 
-    test("is comma-separated", () {
+    test("has an undecided separator", () {
       expect(value.separator, equals(ListSeparator.comma));
     });
 
@@ -143,8 +143,8 @@ main() {
     SassMap value;
     setUp(() => value = parseValue("map-remove((a: b), a)") as SassMap);
 
-    test("is comma-separated", () {
-      expect(value.separator, equals(ListSeparator.comma));
+    test("has an undecided separator", () {
+      expect(value.separator, equals(ListSeparator.undecided));
     });
 
     test("returns its contents as a map", () {
diff --git a/tool/grind/npm.dart b/tool/grind/npm.dart
index 1b77d9cc..8ab71e44 100644
--- a/tool/grind/npm.dart
+++ b/tool/grind/npm.dart
@@ -40,7 +40,10 @@ void _js({@required bool release}) {
     // * We expect our test coverage to ensure that nothing throws subtypes of
     //   Error.
     // * We thoroughly test edge cases in user input.
-    if (release) ...["-O4", "--fast-startup"]
+    //
+    // We don't minify because download size isn't especially important
+    // server-side and it's nice to get readable stack traces from bug reports.
+    if (release) ...["-O4", "--no-minify", "--fast-startup"]
   ]);
   var text = destination
       .readAsStringSync()
diff --git a/tool/travis/task/specs.sh b/tool/travis/task/specs.sh
index c30c14d2..565048e7 100755
--- a/tool/travis/task/specs.sh
+++ b/tool/travis/task/specs.sh
@@ -4,5 +4,5 @@
 # https://opensource.org/licenses/MIT.
 
 echo "$(tput bold)Running sass-spec against $(dart --version &> /dev/stdout).$(tput sgr0)"
-if [ "$ASYNC" = true ]; then extra_args="--dart-args --async"; fi
+if [ "$ASYNC" = true ]; then extra_args="--cmd-args --async"; fi
 (cd sass-spec; bundle exec sass-spec.rb --dart .. $extra_args)