diff --git a/Source/d_deh.c b/Source/d_deh.c
index da7b971a..d15c78e2 100644
--- a/Source/d_deh.c
+++ b/Source/d_deh.c
@@ -2575,7 +2575,7 @@ boolean deh_procStringSub(char *key, char *lookfor, char *newstring, FILE *fpout
           if (!key)
             if (fpout) fprintf(fpout,
                                "Assigned '%.12s%s' to'%.12s%s' at key %s\n",
-                               lookfor, (strlen(lookfor) > 12) ? "..." : "",
+                               lookfor ? : "", (lookfor && strlen(lookfor) > 12) ? "..." : "",
                                newstring, (strlen(newstring) > 12) ? "..." :"",
                                deh_strlookup[i].lookup);