diff --git a/builtin/grep.c b/builtin/grep.c
index 8af5249a7b..fd184c182a 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -199,8 +199,8 @@ static void *run(void *arg)
 		grep_source_clear_data(&w->source);
 		work_done(w);
 	}
-	free_grep_patterns(arg);
-	free(arg);
+	free_grep_patterns(opt);
+	free(opt);
 
 	return (void*) (intptr_t) hit;
 }