diff --git a/src/proxy/proxy_data.go b/src/proxy/proxy_data.go
index 233833a..5b21b73 100644
--- a/src/proxy/proxy_data.go
+++ b/src/proxy/proxy_data.go
@@ -47,15 +47,19 @@ func (proxyData ProxyData) BackendUrls() []string {
 
 func (proxyData *ProxyData) cleanBackend(url string) {
 	proxyData.mutex.Lock()
-	proxyData.Deads[url] = proxyData.Backends[url]
-	delete(proxyData.Backends, url)
+	if backEnd, isHas := proxyData.Backends[url]; isHas {
+		proxyData.Deads[url] = backEnd
+		delete(proxyData.Backends, url)
+	}
 	defer proxyData.mutex.Unlock()
 }
 
 func (proxyData *ProxyData) cleanDeadend(url string) {
 	proxyData.mutex.Lock()
-	proxyData.Backends[url] = proxyData.Deads[url]
-	delete(proxyData.Deads, url)
+	if backEnd, isHas := proxyData.Deads[url]; isHas {
+		proxyData.Backends[url] = backEnd
+		delete(proxyData.Deads, url)
+	}
 	defer proxyData.mutex.Unlock()
 }