Index: generic/nsf.c
===================================================================
diff -u -r0aabdb6234b43933aee2b26d86401912d9db8d48 -rdcbc76a21438ded169203312acee5a924c49dffc
--- generic/nsf.c	(.../nsf.c)	(revision 0aabdb6234b43933aee2b26d86401912d9db8d48)
+++ generic/nsf.c	(.../nsf.c)	(revision dcbc76a21438ded169203312acee5a924c49dffc)
@@ -22964,6 +22964,8 @@
   nonnull_assert(mapvalue != NULL);
   nonnull_assert(outputincr != NULL);
 
+  assert(objc >= 1);
+
   totalargs = objc + tcd->nr_args - 1;
   /*
    * Per default every ForwardArgString from the processed list corresponds to
@@ -23020,6 +23022,9 @@
     char        c1, *firstActualArgument = nrArgs > 0 ? ObjStr(objv[1]) : NULL;
     const char *c1Ptr;
 
+    assert(nrPosArgs >= 0);
+    assert(nrArgs >= 0);
+
     c = *++ForwardArgString;
     c1Ptr = ForwardArgString + 1;
     c1 = *c1Ptr;