diff --git a/pkg/dev_compiler/lib/src/codegen/js_codegen.dart b/pkg/dev_compiler/lib/src/codegen/js_codegen.dart
index e9389cc8570c..824fc0182929 100644
--- a/pkg/dev_compiler/lib/src/codegen/js_codegen.dart
+++ b/pkg/dev_compiler/lib/src/codegen/js_codegen.dart
@@ -885,23 +885,25 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
 
     var body = [];
     for (var param in parameters.parameters) {
-      // TODO(justinfagnani): rename identifier if necessary
-      var name = param.identifier.name;
+      var jsParam = _visit(param.identifier);
 
       if (param.kind == ParameterKind.NAMED) {
+        // Parameters will be passed using their real names, not the (possibly
+        // renamed) local variable.
+        var paramName = js.string(param.identifier.name, "'");
         body.add(js.statement('let # = # && # in # ? #.# : #;', [
-          name,
+          jsParam,
           _namedArgTemp,
-          js.string(name, "'"),
+          paramName,
           _namedArgTemp,
           _namedArgTemp,
-          name,
+          paramName,
           _defaultParamValue(param),
         ]));
       } else if (param.kind == ParameterKind.POSITIONAL) {
         body.add(js.statement('if (# === void 0) # = #;', [
-          name,
-          name,
+          jsParam,
+          jsParam,
           _defaultParamValue(param)
         ]));
       }
diff --git a/pkg/dev_compiler/test/codegen/expect/temps.js b/pkg/dev_compiler/test/codegen/expect/temps.js
index 821b41bedc87..c873da0999dd 100644
--- a/pkg/dev_compiler/test/codegen/expect/temps.js
+++ b/pkg/dev_compiler/test/codegen/expect/temps.js
@@ -11,11 +11,27 @@ var temps;
       this[_function] = func;
     }
   }
+  let _opt = Symbol('_opt');
+  class OptionalArg extends core.Object {
+    OptionalArg(opt) {
+      if (opt === void 0)
+        opt = 123;
+      this[_opt] = opt;
+    }
+    named(opts) {
+      let opt = opts && '_opt' in opts ? opts._opt : 456;
+      this[_opt] = opt;
+    }
+  }
+  dart.defineNamedConstructor(OptionalArg, 'named');
   // Function main: () → dynamic
   function main() {
     core.print(new FormalCollision(1, 2, x => x));
+    core.print(new OptionalArg()[_opt]);
+    core.print(new OptionalArg.named()[_opt]);
   }
   // Exports:
   exports.FormalCollision = FormalCollision;
+  exports.OptionalArg = OptionalArg;
   exports.main = main;
 })(temps || (temps = {}));
diff --git a/pkg/dev_compiler/test/codegen/temps.dart b/pkg/dev_compiler/test/codegen/temps.dart
index 833874c44a4e..cb63c0a6cf3b 100644
--- a/pkg/dev_compiler/test/codegen/temps.dart
+++ b/pkg/dev_compiler/test/codegen/temps.dart
@@ -10,6 +10,14 @@ class FormalCollision {
   FormalCollision(this._x, this.__x, this._function);
 }
 
+class OptionalArg {
+  int _opt;
+  OptionalArg([this._opt = 123]);
+  OptionalArg.named({this._opt: 456});
+}
+
 main() {
   print(new FormalCollision(1, 2, (x) => x));
+  print(new OptionalArg()._opt);
+  print(new OptionalArg.named()._opt);
 }