diff --git a/jdk/src/share/classes/sun/awt/AppContext.java b/jdk/src/share/classes/sun/awt/AppContext.java
index 0370f8333a3..901be0b9a1b 100644
--- a/jdk/src/share/classes/sun/awt/AppContext.java
+++ b/jdk/src/share/classes/sun/awt/AppContext.java
@@ -146,7 +146,9 @@ public final class AppContext {
      * Returns a set containing all <code>AppContext</code>s.
      */
     public static Set<AppContext> getAppContexts() {
-        return new HashSet<AppContext>(threadGroup2appContext.values());
+        synchronized (threadGroup2appContext) {
+            return new HashSet<AppContext>(threadGroup2appContext.values());
+        }
     }
 
     /* The main "system" AppContext, used by everything not otherwise