diff --git a/libraries/ESP8266WiFi/src/WiFiClient.cpp b/libraries/ESP8266WiFi/src/WiFiClient.cpp
index e4b2d1d73..828cbccf3 100644
--- a/libraries/ESP8266WiFi/src/WiFiClient.cpp
+++ b/libraries/ESP8266WiFi/src/WiFiClient.cpp
@@ -156,7 +156,7 @@ bool WiFiClient::getNoDelay() {
 
 size_t WiFiClient::availableForWrite ()
 {
-    return _client->availableForWrite();
+    return _client? _client->availableForWrite(): 0;
 }
 
 size_t WiFiClient::write(uint8_t b)