--- old/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/calc/IsNullNode.java	2017-11-03 23:57:10.599527928 -0700
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/calc/IsNullNode.java	2017-11-03 23:57:10.272513294 -0700
@@ -121,7 +121,8 @@
 
     @Override
     public Stamp getSucceedingStampForValue(boolean negated) {
-        AbstractPointerStamp pointerStamp = (AbstractPointerStamp) getValue().stamp();
+        // Ignore any more precise input stamp since canonicalization will skip through PiNodes
+        AbstractPointerStamp pointerStamp = (AbstractPointerStamp) getValue().stamp().unrestricted();
         return negated ? pointerStamp.asNonNull() : pointerStamp.asAlwaysNull();
     }