diff --git a/lib/roken/warnerr.c b/lib/roken/warnerr.c
index 057fc23c7..89c04fe0d 100644
--- a/lib/roken/warnerr.c
+++ b/lib/roken/warnerr.c
@@ -51,7 +51,10 @@ void
 set_progname(char *argv0)
 {
 #ifndef HAVE___PROGNAME
-    char *p = strrchr(argv0, '/');
+    char *p;
+    if(argv == NULL)
+	return;
+    p = strrchr(argv0, '/');
     if(p == NULL)
 	p = argv0;
     else