diff --git a/.hgignore b/.hgignore
--- a/.hgignore
+++ b/.hgignore
@@ -7,3 +7,6 @@
 ^make/netbeans/.*/dist/
 ^.hgtip
 .DS_Store
+.idea
+.*.iml
+^out/
diff --git a/src/java.base/share/classes/java/lang/invoke/MethodTypeForm.java b/src/java.base/share/classes/java/lang/invoke/MethodTypeForm.java
--- a/src/java.base/share/classes/java/lang/invoke/MethodTypeForm.java
+++ b/src/java.base/share/classes/java/lang/invoke/MethodTypeForm.java
@@ -114,7 +114,7 @@
         // Simulate a CAS, to avoid racy duplication of results.
         MethodHandle prev = methodHandles[which];
         if (prev != null)  return prev;
-        return methodHandles[which] = mh;
+        return mh;
     }
 
     public LambdaForm cachedLambdaForm(int which) {
@@ -126,7 +126,7 @@
         // Simulate a CAS, to avoid racy duplication of results.
         LambdaForm prev = lambdaForms[which];
         if (prev != null) return prev;
-        return lambdaForms[which] = form;
+        return form;
     }
 
     /**