diff --git a/WebViewJavascriptBridge/WKWebViewJavascriptBridge.m b/WebViewJavascriptBridge/WKWebViewJavascriptBridge.m
index 47667df6..0d97b6e7 100644
--- a/WebViewJavascriptBridge/WKWebViewJavascriptBridge.m
+++ b/WebViewJavascriptBridge/WKWebViewJavascriptBridge.m
@@ -147,6 +147,8 @@ - (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigati
             [_base logUnkownMessage:url];
         }
         decisionHandler(WKNavigationActionPolicyCancel);
+        // fix ios11 crash.
+        return;
     }
     
     if (strongDelegate && [strongDelegate respondsToSelector:@selector(webView:decidePolicyForNavigationAction:decisionHandler:)]) {