src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/calc/IsNullNode.java

@@ -119,11 +119,12 @@
         }
     }
 
     @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();
     }
 
     @Override
     public TriState tryFold(Stamp valueStamp) {