--- old/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.graph/src/org/graalvm/compiler/graph/CachedGraph.java	2017-07-07 09:29:58.000000000 -0700
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.graph/src/org/graalvm/compiler/graph/CachedGraph.java	2017-07-07 09:29:58.000000000 -0700
@@ -62,7 +62,9 @@
     @SuppressWarnings("unchecked")
     public G getMutableCopy(Consumer<UnmodifiableEconomicMap<Node, Node>> duplicationMapCallback) {
         if (!hasMutableCopy()) {
-            mutableCopy = (G) readonlyCopy.copy(duplicationMapCallback);
+            // Sharing the debug context with the copy is safe since both graphs are
+            // only used in the current thread.
+            mutableCopy = (G) readonlyCopy.copy(duplicationMapCallback, readonlyCopy.getDebug());
         }
         return mutableCopy;
     }