diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/ChameleonJsExpression.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/ChameleonJsExpression.java
index c50d40e8166..df2171ce1aa 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/ChameleonJsExpression.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/ChameleonJsExpression.java
@@ -1,5 +1,7 @@
 package com.google.dart.compiler.backend.js.ast;
 
+import org.jetbrains.annotations.NotNull;
+
 public class ChameleonJsExpression implements JsExpression {
     private JsExpression expression;
 
@@ -20,6 +22,7 @@ public class ChameleonJsExpression implements JsExpression {
     }
 
     @Override
+    @NotNull
     public JsStatement makeStmt() {
         return expression.makeStmt();
     }
diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpression.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpression.java
index 5209a21eb64..b2486988cc7 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpression.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpression.java
@@ -1,8 +1,11 @@
 package com.google.dart.compiler.backend.js.ast;
 
+import org.jetbrains.annotations.NotNull;
+
 public interface JsExpression extends JsNode {
     boolean isLeaf();
 
+    @NotNull
     JsStatement makeStmt();
 
     @Override
diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpressionImpl.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpressionImpl.java
index f1f5bed3399..d26bc03f2a6 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpressionImpl.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsExpressionImpl.java
@@ -4,6 +4,8 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
+import org.jetbrains.annotations.NotNull;
+
 import java.util.List;
 
 abstract class JsExpressionImpl extends SourceInfoAwareJsNode implements JsExpression {
@@ -20,6 +22,7 @@ abstract class JsExpressionImpl extends SourceInfoAwareJsNode implements JsExpre
     }
 
     @Override
+    @NotNull
     public JsStatement makeStmt() {
         return new JsExpressionStatement(this);
     }
diff --git a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsProgram.java b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsProgram.java
index 6a388acf669..b39e764b23d 100644
--- a/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsProgram.java
+++ b/js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsProgram.java
@@ -18,6 +18,7 @@ import static com.google.dart.compiler.backend.js.ast.JsNumberLiteral.JsIntLiter
  * A JavaScript program.
  */
 public final class JsProgram extends SourceInfoAwareJsNode {
+    @NotNull
     private final JsEmpty emptyStatement;
 
     private JsProgramFragment[] fragments;
@@ -37,6 +38,7 @@ public final class JsProgram extends SourceInfoAwareJsNode {
         emptyStatement = new JsEmpty();
     }
 
+    @NotNull
     public JsEmpty getEmptyStatement() {
         return emptyStatement;
     }