diff --git a/jps/jps-builders/src/org/jetbrains/jps/javac/ast/RefCollectorCompilerToolExtension.java b/jps/jps-builders/src/org/jetbrains/jps/javac/ast/RefCollectorCompilerToolExtension.java
index 6685b63403f4..e45c0dd9021a 100644
--- a/jps/jps-builders/src/org/jetbrains/jps/javac/ast/RefCollectorCompilerToolExtension.java
+++ b/jps/jps-builders/src/org/jetbrains/jps/javac/ast/RefCollectorCompilerToolExtension.java
@@ -31,6 +31,7 @@ import java.util.Collection;
 public class RefCollectorCompilerToolExtension extends JavaCompilerToolExtension{
   public static final String ID = "ASTReferenceCollector";
 
+  @NotNull
   @Override
   public String getId() {
     return ID;