diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatch.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatch.java
index 4cd48e11a02..cdc1d13f305 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatch.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatch.java
@@ -17,7 +17,7 @@ public class JsCatch extends SourceInfoAwareJsNode implements HasCondition {
     private JsExpression condition;
     private JsParameter param;
 
-    public JsCatch(JsScope parent, String ident) {
+    public JsCatch(JsScope parent, @NotNull String ident) {
         super();
         assert (parent != null);
         scope = new JsCatchScope(parent, ident);
diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatchScope.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatchScope.java
index 671f4dd0daf..afa4115f641 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatchScope.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsCatchScope.java
@@ -13,7 +13,7 @@ import org.jetbrains.annotations.NotNull;
 public class JsCatchScope extends JsScope {
     private final JsName name;
 
-    public JsCatchScope(JsScope parent, String ident) {
+    public JsCatchScope(JsScope parent, @NotNull String ident) {
         super(parent, "Catch scope", null);
         name = new JsName(this, ident);
     }
diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsName.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsName.java
index b58099cd680..ab19d383c1b 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsName.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsName.java
@@ -13,16 +13,19 @@ import org.jetbrains.annotations.NotNull;
  */
 public class JsName extends HasMetadata implements Symbol {
   private final JsScope enclosing;
+
+  @NotNull
   private final String ident;
 
   /**
    * @param ident the unmangled ident to use for this name
    */
-  JsName(JsScope enclosing, String ident) {
+  JsName(JsScope enclosing, @NotNull String ident) {
     this.enclosing = enclosing;
     this.ident = ident;
   }
 
+  @NotNull
   public String getIdent() {
     return ident;
   }
diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsScope.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsScope.java
index 01ddf652872..392d82db557 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsScope.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsScope.java
@@ -166,7 +166,7 @@ public abstract class JsScope {
     }
 
     @NotNull
-    protected JsName doCreateName(String ident) {
+    protected JsName doCreateName(@NotNull String ident) {
         JsName name = new JsName(this, ident);
         names = Maps.put(names, ident, name);
         return name;