Index: clang/lib/StaticAnalyzer/Checkers/IteratorRangeChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/IteratorRangeChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/IteratorRangeChecker.cpp
@@ -228,7 +228,7 @@
     Value = State->getRawSVal(*ValAsLoc);
   }
 
-  if (Value.isUnknown())
+  if (Value.isUnknownOrUndef())
     return;
 
   // Incremention or decremention by 0 is never a bug.