diff --git a/lib/src/ast/css/at_rule.dart b/lib/src/ast/css/at_rule.dart
index 2564c8ca..864d8751 100644
--- a/lib/src/ast/css/at_rule.dart
+++ b/lib/src/ast/css/at_rule.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
@@ -18,4 +19,6 @@ abstract class CssAtRule extends CssParentNode {
   /// This implies `children.isEmpty`, but the reverse is not true—for a rule
   /// like `@foo {}`, [children] is empty but [isChildless] is `false`.
   bool get isChildless;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssAtRule(this);
 }
diff --git a/lib/src/ast/css/comment.dart b/lib/src/ast/css/comment.dart
index 6c8b8017..4724a83b 100644
--- a/lib/src/ast/css/comment.dart
+++ b/lib/src/ast/css/comment.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import 'node.dart';
 
 /// A plain CSS comment.
@@ -14,4 +15,6 @@ abstract class CssComment extends CssNode {
   /// Whether this comment starts with `/*!` and so should be preserved even in
   /// compressed mode.
   bool get isPreserved;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssComment(this);
 }
diff --git a/lib/src/ast/css/declaration.dart b/lib/src/ast/css/declaration.dart
index 51558cb3..01b26c3a 100644
--- a/lib/src/ast/css/declaration.dart
+++ b/lib/src/ast/css/declaration.dart
@@ -5,6 +5,7 @@
 import 'package:source_span/source_span.dart';
 
 import '../../value.dart';
+import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
@@ -22,4 +23,6 @@ abstract class CssDeclaration extends CssNode {
   /// where that variable was declared whereas [value.span] is the span where
   /// the variable was used. Otherwise, this is identical to [value.span].
   FileSpan get valueSpanForMap;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssDeclaration(this);
 }
diff --git a/lib/src/ast/css/import.dart b/lib/src/ast/css/import.dart
index fcefc003..065ef076 100644
--- a/lib/src/ast/css/import.dart
+++ b/lib/src/ast/css/import.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import 'media_query.dart';
 import 'node.dart';
 import 'value.dart';
@@ -18,4 +19,6 @@ abstract class CssImport extends CssNode {
 
   /// The media query attached to this import.
   List<CssMediaQuery> get media;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssImport(this);
 }
diff --git a/lib/src/ast/css/keyframe_block.dart b/lib/src/ast/css/keyframe_block.dart
index e85e3e08..0b52cd82 100644
--- a/lib/src/ast/css/keyframe_block.dart
+++ b/lib/src/ast/css/keyframe_block.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
@@ -11,4 +12,6 @@ import 'value.dart';
 abstract class CssKeyframeBlock extends CssParentNode {
   /// The selector for this block.
   CssValue<List<String>> get selector;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssKeyframeBlock(this);
 }
diff --git a/lib/src/ast/css/media_rule.dart b/lib/src/ast/css/media_rule.dart
index affcca8b..d44859fb 100644
--- a/lib/src/ast/css/media_rule.dart
+++ b/lib/src/ast/css/media_rule.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import 'media_query.dart';
 import 'node.dart';
 
@@ -11,4 +12,6 @@ abstract class CssMediaRule extends CssParentNode {
   ///
   /// This is never empty.
   List<CssMediaQuery> get queries;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssMediaRule(this);
 }
diff --git a/lib/src/ast/css/modifiable/at_rule.dart b/lib/src/ast/css/modifiable/at_rule.dart
index 990ef840..4a4f3ce6 100644
--- a/lib/src/ast/css/modifiable/at_rule.dart
+++ b/lib/src/ast/css/modifiable/at_rule.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../at_rule.dart';
 import '../value.dart';
 import 'node.dart';
@@ -20,7 +20,7 @@ class ModifiableCssAtRule extends ModifiableCssParentNode implements CssAtRule {
       {bool childless = false, this.value})
       : isChildless = childless;
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssAtRule(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) => visitor.visitCssAtRule(this);
 
   ModifiableCssAtRule copyWithoutChildren() =>
       ModifiableCssAtRule(name, span, childless: isChildless, value: value);
diff --git a/lib/src/ast/css/modifiable/comment.dart b/lib/src/ast/css/modifiable/comment.dart
index 3ea3d151..40e7838c 100644
--- a/lib/src/ast/css/modifiable/comment.dart
+++ b/lib/src/ast/css/modifiable/comment.dart
@@ -5,7 +5,7 @@
 import 'package:charcode/charcode.dart';
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../comment.dart';
 import 'node.dart';
 
@@ -18,5 +18,5 @@ class ModifiableCssComment extends ModifiableCssNode implements CssComment {
 
   ModifiableCssComment(this.text, this.span);
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssComment(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) => visitor.visitCssComment(this);
 }
diff --git a/lib/src/ast/css/modifiable/declaration.dart b/lib/src/ast/css/modifiable/declaration.dart
index b9910848..fb7dc2b3 100644
--- a/lib/src/ast/css/modifiable/declaration.dart
+++ b/lib/src/ast/css/modifiable/declaration.dart
@@ -5,7 +5,7 @@
 import 'package:source_span/source_span.dart';
 
 import '../../../value.dart';
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../declaration.dart';
 import '../value.dart';
 import 'node.dart';
@@ -22,5 +22,6 @@ class ModifiableCssDeclaration extends ModifiableCssNode
       {FileSpan valueSpanForMap})
       : valueSpanForMap = valueSpanForMap ?? span;
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssDeclaration(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) =>
+      visitor.visitCssDeclaration(this);
 }
diff --git a/lib/src/ast/css/modifiable/import.dart b/lib/src/ast/css/modifiable/import.dart
index 0e5d9eb4..cf8127ff 100644
--- a/lib/src/ast/css/modifiable/import.dart
+++ b/lib/src/ast/css/modifiable/import.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../import.dart';
 import '../media_query.dart';
 import '../value.dart';
@@ -29,5 +29,5 @@ class ModifiableCssImport extends ModifiableCssNode implements CssImport {
       {this.supports, Iterable<CssMediaQuery> media})
       : media = media == null ? null : List.unmodifiable(media);
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssImport(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) => visitor.visitCssImport(this);
 }
diff --git a/lib/src/ast/css/modifiable/keyframe_block.dart b/lib/src/ast/css/modifiable/keyframe_block.dart
index 96383bbb..69233f35 100644
--- a/lib/src/ast/css/modifiable/keyframe_block.dart
+++ b/lib/src/ast/css/modifiable/keyframe_block.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../keyframe_block.dart';
 import '../value.dart';
 import 'node.dart';
@@ -17,7 +17,8 @@ class ModifiableCssKeyframeBlock extends ModifiableCssParentNode
 
   ModifiableCssKeyframeBlock(this.selector, this.span);
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssKeyframeBlock(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) =>
+      visitor.visitCssKeyframeBlock(this);
 
   ModifiableCssKeyframeBlock copyWithoutChildren() =>
       ModifiableCssKeyframeBlock(selector, span);
diff --git a/lib/src/ast/css/modifiable/media_rule.dart b/lib/src/ast/css/modifiable/media_rule.dart
index 385fb5c3..f1dcf25e 100644
--- a/lib/src/ast/css/modifiable/media_rule.dart
+++ b/lib/src/ast/css/modifiable/media_rule.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../media_query.dart';
 import '../media_rule.dart';
 import 'node.dart';
@@ -22,7 +22,8 @@ class ModifiableCssMediaRule extends ModifiableCssParentNode
     }
   }
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssMediaRule(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) =>
+      visitor.visitCssMediaRule(this);
 
   ModifiableCssMediaRule copyWithoutChildren() =>
       ModifiableCssMediaRule(queries, span);
diff --git a/lib/src/ast/css/modifiable/node.dart b/lib/src/ast/css/modifiable/node.dart
index 5cd33c1a..61e11883 100644
--- a/lib/src/ast/css/modifiable/node.dart
+++ b/lib/src/ast/css/modifiable/node.dart
@@ -4,7 +4,7 @@
 
 import 'dart:collection';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../at_rule.dart';
 import '../node.dart';
 import '../style_rule.dart';
@@ -57,7 +57,7 @@ abstract class ModifiableCssNode extends CssNode {
     }
   }
 
-  T accept<T>(CssVisitor<T> visitor);
+  T accept<T>(ModifiableCssVisitor<T> visitor);
 
   /// Removes [this] from [parent]'s child list.
   ///
diff --git a/lib/src/ast/css/modifiable/style_rule.dart b/lib/src/ast/css/modifiable/style_rule.dart
index 78ef3a10..a342abee 100644
--- a/lib/src/ast/css/modifiable/style_rule.dart
+++ b/lib/src/ast/css/modifiable/style_rule.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../../selector.dart';
 import '../style_rule.dart';
 import 'node.dart';
@@ -28,7 +28,8 @@ class ModifiableCssStyleRule extends ModifiableCssParentNode
       : selector = selector,
         originalSelector = originalSelector ?? selector.value;
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssStyleRule(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) =>
+      visitor.visitCssStyleRule(this);
 
   ModifiableCssStyleRule copyWithoutChildren() =>
       ModifiableCssStyleRule(selector, span,
diff --git a/lib/src/ast/css/modifiable/stylesheet.dart b/lib/src/ast/css/modifiable/stylesheet.dart
index 25f2505a..46610a94 100644
--- a/lib/src/ast/css/modifiable/stylesheet.dart
+++ b/lib/src/ast/css/modifiable/stylesheet.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../stylesheet.dart';
 import 'node.dart';
 
@@ -15,7 +15,8 @@ class ModifiableCssStylesheet extends ModifiableCssParentNode
 
   ModifiableCssStylesheet(this.span);
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssStylesheet(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) =>
+      visitor.visitCssStylesheet(this);
 
   ModifiableCssStylesheet copyWithoutChildren() =>
       ModifiableCssStylesheet(span);
diff --git a/lib/src/ast/css/modifiable/supports_rule.dart b/lib/src/ast/css/modifiable/supports_rule.dart
index f344d5fa..ef921b51 100644
--- a/lib/src/ast/css/modifiable/supports_rule.dart
+++ b/lib/src/ast/css/modifiable/supports_rule.dart
@@ -4,7 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
-import '../../../visitor/interface/css.dart';
+import '../../../visitor/interface/modifiable_css.dart';
 import '../supports_rule.dart';
 import '../value.dart';
 import 'node.dart';
@@ -17,7 +17,8 @@ class ModifiableCssSupportsRule extends ModifiableCssParentNode
 
   ModifiableCssSupportsRule(this.condition, this.span);
 
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssSupportsRule(this);
+  T accept<T>(ModifiableCssVisitor<T> visitor) =>
+      visitor.visitCssSupportsRule(this);
 
   ModifiableCssSupportsRule copyWithoutChildren() =>
       ModifiableCssSupportsRule(condition, span);
diff --git a/lib/src/ast/css/style_rule.dart b/lib/src/ast/css/style_rule.dart
index 53b134f5..063a9e28 100644
--- a/lib/src/ast/css/style_rule.dart
+++ b/lib/src/ast/css/style_rule.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import '../selector.dart';
 import 'node.dart';
 import 'value.dart';
@@ -14,4 +15,6 @@ import 'value.dart';
 abstract class CssStyleRule extends CssParentNode {
   /// The selector for this rule.
   CssValue<SelectorList> get selector;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssStyleRule(this);
 }
diff --git a/lib/src/ast/css/supports_rule.dart b/lib/src/ast/css/supports_rule.dart
index 0c63cbb8..091ba1da 100644
--- a/lib/src/ast/css/supports_rule.dart
+++ b/lib/src/ast/css/supports_rule.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
@@ -9,4 +10,6 @@ import 'value.dart';
 abstract class CssSupportsRule extends CssParentNode {
   /// The supports condition.
   CssValue<String> get condition;
+
+  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssSupportsRule(this);
 }
diff --git a/lib/src/visitor/interface/css.dart b/lib/src/visitor/interface/css.dart
index 4f609546..06485582 100644
--- a/lib/src/visitor/interface/css.dart
+++ b/lib/src/visitor/interface/css.dart
@@ -3,11 +3,12 @@
 // https://opensource.org/licenses/MIT.
 
 import '../../ast/css.dart';
+import 'modifiable_css.dart';
 
 /// An interface for [visitors][] that traverse CSS statements.
 ///
 /// [visitors]: https://en.wikipedia.org/wiki/Visitor_pattern
-abstract class CssVisitor<T> {
+abstract class CssVisitor<T> implements ModifiableCssVisitor<T> {
   T visitCssAtRule(CssAtRule node);
   T visitCssComment(CssComment node);
   T visitCssDeclaration(CssDeclaration node);
diff --git a/lib/src/visitor/interface/modifiable_css.dart b/lib/src/visitor/interface/modifiable_css.dart
new file mode 100644
index 00000000..643dc9b0
--- /dev/null
+++ b/lib/src/visitor/interface/modifiable_css.dart
@@ -0,0 +1,20 @@
+// Copyright 2019 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import '../../ast/css/modifiable.dart';
+
+/// An interface for [visitors][] that traverse CSS statements.
+///
+/// [visitors]: https://en.wikipedia.org/wiki/Visitor_pattern
+abstract class ModifiableCssVisitor<T> {
+  T visitCssAtRule(ModifiableCssAtRule node);
+  T visitCssComment(ModifiableCssComment node);
+  T visitCssDeclaration(ModifiableCssDeclaration node);
+  T visitCssImport(ModifiableCssImport node);
+  T visitCssKeyframeBlock(ModifiableCssKeyframeBlock node);
+  T visitCssMediaRule(ModifiableCssMediaRule node);
+  T visitCssStyleRule(ModifiableCssStyleRule node);
+  T visitCssStylesheet(ModifiableCssStylesheet node);
+  T visitCssSupportsRule(ModifiableCssSupportsRule node);
+}