diff --git a/clients/ud/auth.c b/clients/ud/auth.c
index 4c191ba2a0..845bffc5a3 100644
--- a/clients/ud/auth.c
+++ b/clients/ud/auth.c
@@ -429,5 +429,5 @@ char *s;
 
 	if (bound_dn != NULL)
 		Free(bound_dn);
-	bound_dn = strdup(s);
+	bound_dn = (s == NULL) ? NULL : strdup(s);
 }