diff --git a/src/Psalm/Checker/FunctionChecker.php b/src/Psalm/Checker/FunctionChecker.php
index 73d874afd..3018192e1 100644
--- a/src/Psalm/Checker/FunctionChecker.php
+++ b/src/Psalm/Checker/FunctionChecker.php
@@ -248,17 +248,23 @@ class FunctionChecker extends FunctionLikeChecker
 
             foreach ($call_map_function_args as $arg_name => $arg_type) {
                 $by_reference = false;
+                $optional = false;
 
                 if ($arg_name[0] === '&') {
                     $arg_name = substr($arg_name, 1);
                     $by_reference = true;
                 }
 
+                if (substr($arg_name, -1) === '=') {
+                    $arg_name = substr($arg_name, 0, -1);
+                    $optional = true;
+                }
+
                 $function_types[] = new FunctionLikeParameter(
                     $arg_name,
                     $by_reference,
                     $arg_type ? Type::parseString($arg_type) : Type::getMixed(),
-                    true // @todo - need to have non-optional parameters
+                    $optional
                 );
             }
 
diff --git a/src/Psalm/Checker/FunctionLikeChecker.php b/src/Psalm/Checker/FunctionLikeChecker.php
index bf144d82c..e1657c6db 100644
--- a/src/Psalm/Checker/FunctionLikeChecker.php
+++ b/src/Psalm/Checker/FunctionLikeChecker.php
@@ -827,8 +827,21 @@ abstract class FunctionLikeChecker implements StatementsSource
 
             $last_param = count($possible_function_params) ? $possible_function_params[count($possible_function_params) - 1] : null;
 
+            $mandatory_param_count = count($possible_function_params);
+
+            foreach ($possible_function_params as $i => $possible_function_param) {
+                if ($possible_function_param->is_optional) {
+                    $mandatory_param_count = $i;
+                    break;
+                }
+            }
+
+            if ($mandatory_param_count > count($args)) {
+                continue;
+            }
+
             foreach ($args as $argument_offset => $arg) {
-                if (count($possible_function_params) <= $argument_offset && (!$last_param || $last_param->name !== '...')) {
+                if (count($possible_function_params) <= $argument_offset && (!$last_param || substr($last_param->name, 0, 3) !== '...')) {
                     $all_args_match = false;
                     break;
                 }