Index: generic/nsf.c
===================================================================
diff -u -rabc49521cdbdd7043375d02dd85baa48526989d5 -r16633463011fcad616e0370fd5fc333a6bbca030
--- generic/nsf.c	(.../nsf.c)	(revision abc49521cdbdd7043375d02dd85baa48526989d5)
+++ generic/nsf.c	(.../nsf.c)	(revision 16633463011fcad616e0370fd5fc333a6bbca030)
@@ -5195,7 +5195,9 @@
       NsfObjectSystem *osPtr;
 
       if ((frameFlags & (FRAME_IS_NSF_METHOD|FRAME_IS_NSF_CMETHOD)) != 0u) {
-        object = ((NsfCallStackContent *)varFramePtr->clientData)->self;
+        NsfCallStackContent *cscPtr = (NsfCallStackContent *)varFramePtr->clientData;
+        assert(cscPtr != NULL);
+        object = cscPtr->self;
       } else if ((frameFlags & (FRAME_IS_NSF_OBJECT)) != 0u) {
         object = (NsfObject *)(varFramePtr->clientData);
       } else {