diff --git a/AppKit/fifo.c b/AppKit/fifo.c
index 47b721b..bb6c94d 100644
--- a/AppKit/fifo.c
+++ b/AppKit/fifo.c
@@ -392,6 +392,9 @@ unsigned long fifo_strtoul(fifo_t* self, os_size_t* endptr /*从哪里开始转
 
 // Returns the virtual index relative to tail where the match starts, or -1 if not found
 os_size_t fifo_strstr(fifo_t *self, const char *search) {
+
+    if(self==NULL || search==NULL || search[0]=='\0') return FIFO_INVALID_POS;
+
     os_size_t search_len = strlen(search);
     os_size_t count = fifo_count(self);
     if (search_len == 0 || count < search_len) return FIFO_INVALID_POS;