diff --git a/cde/programs/dtappbuilder/src/libAButil/istr.h b/cde/programs/dtappbuilder/src/libAButil/istr.h
index fead77a60..358281484 100644
--- a/cde/programs/dtappbuilder/src/libAButil/istr.h
+++ b/cde/programs/dtappbuilder/src/libAButil/istr.h
@@ -272,7 +272,7 @@ extern ISTR_PRIVT_STRN	*istrP_int_array1809065681PrivD;
 #define istr_string_safe(s) ((s) == NULL? Istr_null_string:istr_string(s))
 
 #define istrP_get_string_fast3718930164PrivF(istring) \
-    (istrP_int_array1809065681PrivD[((int)istring)].str)
+    ((istring)==NULL ? Istr_null_string : (istrP_int_array1809065681PrivD[((long)istring)].str))
 
 /* istr_string - if debugging is turned on, checks ISTRINGS for validity */
 #ifdef DEBUG