diff --git a/lib/grammar.js b/lib/grammar.js
index 15565411..15134bed 100644
--- a/lib/grammar.js
+++ b/lib/grammar.js
@@ -468,7 +468,7 @@
         return new WhileNode($2);
       }), o("WHILE Expression WHEN Expression", function() {
         return new WhileNode($2, {
-          filter: $4
+          guard: $4
         });
       })
     ],
@@ -514,7 +514,7 @@
         return [$1, $3];
       })
     ],
-    // The source of a comprehension is an array or object with an optional filter
+    // The source of a comprehension is an array or object with an optional guard
     // clause. If it's an array comprehension, you can also choose to step through
     // in fixed-size increments.
     ForSource: [
@@ -530,12 +530,12 @@
       }), o("IN Expression WHEN Expression", function() {
         return {
           source: $2,
-          filter: $4
+          guard: $4
         };
       }), o("OF Expression WHEN Expression", function() {
         return {
           source: $2,
-          filter: $4,
+          guard: $4,
           object: true
         };
       }), o("IN Expression BY Expression", function() {
@@ -546,14 +546,14 @@
       }), o("IN Expression WHEN Expression BY Expression", function() {
         return {
           source: $2,
-          filter: $4,
+          guard: $4,
           step: $6
         };
       }), o("IN Expression BY Expression WHEN Expression", function() {
         return {
           source: $2,
           step: $4,
-          filter: $6
+          guard: $6
         };
       })
     ],
diff --git a/lib/nodes.js b/lib/nodes.js
index 69cfd5f4..88675287 100644
--- a/lib/nodes.js
+++ b/lib/nodes.js
@@ -1177,7 +1177,7 @@
   exports.WhileNode = (function() {
     WhileNode = function WhileNode(condition, opts) {
       this.children = [(this.condition = condition)];
-      this.filter = opts && opts.filter;
+      this.guard = opts && opts.guard;
       return this;
     };
     __extends(WhileNode, BaseNode);
@@ -1213,8 +1213,8 @@
       if (!this.body) {
         return ("" + pre + " null;" + post);
       }
-      if (this.filter) {
-        this.body = Expressions.wrap([new IfNode(this.filter, this.body)]);
+      if (this.guard) {
+        this.body = Expressions.wrap([new IfNode(this.guard, this.body)]);
       }
       this.returns ? (post = new ReturnNode(literal(rvar)).compile(merge(o, {
         indent: this.idt()
@@ -1460,7 +1460,7 @@
       this.name = name;
       this.index = index || null;
       this.source = source.source;
-      this.filter = source.filter;
+      this.guard = source.guard;
       this.step = source.step;
       this.object = !!source.object;
       if (this.object) {
@@ -1472,7 +1472,7 @@
       if (this.index instanceof ValueNode) {
         throw new Error('index cannot be a pattern matching expression');
       }
-      this.children = compact([this.body, this.source, this.filter]);
+      this.children = compact([this.body, this.source, this.guard]);
       this.returns = false;
       return this;
     };
@@ -1551,7 +1551,7 @@
       if (!(top_level)) {
         body = PushNode.wrap(rvar, body);
       }
-      this.filter ? (body = Expressions.wrap([new IfNode(this.filter, body)])) : null;
+      this.guard ? (body = Expressions.wrap([new IfNode(this.guard, body)])) : null;
       this.object ? (for_part = ("" + ivar + " in " + svar + ") { if (" + (utility('hasProp')) + ".call(" + svar + ", " + ivar + ")")) : null;
       body = body.compile(merge(o, {
         indent: body_dent,
diff --git a/lib/parser.js b/lib/parser.js
index dff64b05..2c609e73 100755
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -294,7 +294,7 @@ break;
 case 139:this.$ = new WhileNode($$[$0-2+2-1]);
 break;
 case 140:this.$ = new WhileNode($$[$0-4+2-1], {
-          filter: $$[$0-4+4-1]
+          guard: $$[$0-4+4-1]
         });
 break;
 case 141:this.$ = $$[$0-2+1-1].add_body($$[$0-2+2-1]);
@@ -330,12 +330,12 @@ case 153:this.$ = {
 break;
 case 154:this.$ = {
           source: $$[$0-4+2-1],
-          filter: $$[$0-4+4-1]
+          guard: $$[$0-4+4-1]
         };
 break;
 case 155:this.$ = {
           source: $$[$0-4+2-1],
-          filter: $$[$0-4+4-1],
+          guard: $$[$0-4+4-1],
           object: true
         };
 break;
@@ -346,14 +346,14 @@ case 156:this.$ = {
 break;
 case 157:this.$ = {
           source: $$[$0-6+2-1],
-          filter: $$[$0-6+4-1],
+          guard: $$[$0-6+4-1],
           step: $$[$0-6+6-1]
         };
 break;
 case 158:this.$ = {
           source: $$[$0-6+2-1],
           step: $$[$0-6+4-1],
-          filter: $$[$0-6+6-1]
+          guard: $$[$0-6+6-1]
         };
 break;
 case 159:this.$ = $$[$0-5+4-1].rewrite_condition($$[$0-5+2-1]);
diff --git a/src/grammar.coffee b/src/grammar.coffee
index f6b399a9..113a4942 100644
--- a/src/grammar.coffee
+++ b/src/grammar.coffee
@@ -413,7 +413,7 @@ grammar: {
   # The condition portion of a while loop.
   WhileSource: [
     o "WHILE Expression",                       -> new WhileNode $2
-    o "WHILE Expression WHEN Expression",       -> new WhileNode $2, {filter : $4}
+    o "WHILE Expression WHEN Expression",       -> new WhileNode $2, {guard : $4}
   ]
 
   # The while loop can either be normal, with a block of expressions to execute,
@@ -449,17 +449,17 @@ grammar: {
     o "ForValue , ForValue",                    -> [$1, $3]
   ]
 
-  # The source of a comprehension is an array or object with an optional filter
+  # The source of a comprehension is an array or object with an optional guard
   # clause. If it's an array comprehension, you can also choose to step through
   # in fixed-size increments.
   ForSource: [
     o "IN Expression",                               -> {source: $2}
     o "OF Expression",                               -> {source: $2, object: true}
-    o "IN Expression WHEN Expression",               -> {source: $2, filter: $4}
-    o "OF Expression WHEN Expression",               -> {source: $2, filter: $4, object: true}
+    o "IN Expression WHEN Expression",               -> {source: $2, guard: $4}
+    o "OF Expression WHEN Expression",               -> {source: $2, guard: $4, object: true}
     o "IN Expression BY Expression",                 -> {source: $2, step:   $4}
-    o "IN Expression WHEN Expression BY Expression", -> {source: $2, filter: $4, step:   $6}
-    o "IN Expression BY Expression WHEN Expression", -> {source: $2, step:   $4, filter: $6}
+    o "IN Expression WHEN Expression BY Expression", -> {source: $2, guard: $4, step:   $6}
+    o "IN Expression BY Expression WHEN Expression", -> {source: $2, step:   $4, guard: $6}
   ]
 
   # The CoffeeScript switch/when/else block replaces the JavaScript
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 45e39b8f..0752a1d8 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -856,7 +856,7 @@ exports.WhileNode: class WhileNode extends BaseNode
 
   constructor: (condition, opts) ->
     @children:[@condition: condition]
-    @filter: opts and opts.filter
+    @guard: opts and opts.guard
 
   add_body: (body) ->
     @children.push @body: body
@@ -884,7 +884,7 @@ exports.WhileNode: class WhileNode extends BaseNode
       @body:    PushNode.wrap(rvar, @body) if @body
     pre:        "$set${@tab}while ($cond)"
     return "$pre null;$post" if not @body
-    @body:      Expressions.wrap([new IfNode(@filter, @body)]) if @filter
+    @body:      Expressions.wrap([new IfNode(@guard, @body)]) if @guard
     if @returns
       post: new ReturnNode(literal(rvar)).compile(merge(o, {indent: @idt()}))
     else
@@ -1078,13 +1078,13 @@ exports.ForNode: class ForNode extends BaseNode
     @name:    name
     @index:   index or null
     @source:  source.source
-    @filter:  source.filter
+    @guard:   source.guard
     @step:    source.step
     @object:  !!source.object
     [@name, @index]: [@index, @name] if @object
     @pattern: @name instanceof ValueNode
     throw new Error('index cannot be a pattern matching expression') if @index instanceof ValueNode
-    @children: compact [@body, @source, @filter]
+    @children: compact [@body, @source, @guard]
     @returns: false
 
   top_sensitive: ->
@@ -1138,8 +1138,8 @@ exports.ForNode: class ForNode extends BaseNode
 
     body:           ClosureNode.wrap(body, true) if top_level and body.contains (n) -> n instanceof CodeNode
     body:           PushNode.wrap(rvar, body) unless top_level
-    if @filter
-      body:         Expressions.wrap([new IfNode(@filter, body)])
+    if @guard
+      body:         Expressions.wrap([new IfNode(@guard, body)])
     if @object
       for_part: "$ivar in $svar) { if (${utility('hasProp')}.call($svar, $ivar)"
     body:           body.compile(merge(o, {indent: body_dent, top: true}))