diff --git a/cores/esp8266/core_esp8266_main.cpp b/cores/esp8266/core_esp8266_main.cpp
index 4d69c2f48..072baf933 100644
--- a/cores/esp8266/core_esp8266_main.cpp
+++ b/cores/esp8266/core_esp8266_main.cpp
@@ -86,6 +86,7 @@ static void loop_task(os_event_t *events)
     cont_run(&g_cont, &loop_wrapper);
     if (cont_check(&g_cont) != 0)
     {
+        ets_printf("\r\nheap collided with sketch stack\r\n");
         abort();
     }
 }
diff --git a/cores/esp8266/debug.h b/cores/esp8266/debug.h
index 902fc7176..24f3cb983 100644
--- a/cores/esp8266/debug.h
+++ b/cores/esp8266/debug.h
@@ -3,7 +3,6 @@
 
 #include <stddef.h>
 
-extern "C" size_t ets_printf(const char*, ...);
 #define DEBUGV ets_printf
 
 
diff --git a/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp b/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp
index ac55dbe53..24f743ac0 100644
--- a/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp
+++ b/libraries/ESP8266WiFi/src/ESP8266WiFi.cpp
@@ -34,7 +34,6 @@ extern "C" {
 extern "C" void esp_schedule();
 extern "C" void esp_yield();
 
-
 ESP8266WiFiClass::ESP8266WiFiClass()
 {
 
diff --git a/libraries/ESP8266WiFi/src/WiFiClient.cpp b/libraries/ESP8266WiFi/src/WiFiClient.cpp
index 214af4e73..fcb30ccd6 100644
--- a/libraries/ESP8266WiFi/src/WiFiClient.cpp
+++ b/libraries/ESP8266WiFi/src/WiFiClient.cpp
@@ -22,6 +22,8 @@
 extern "C" 
 {
     #include "include/wl_definitions.h"
+    #include "osapi.h"
+    #include "ets_sys.h"
 }
 
 #include "debug.h"
diff --git a/libraries/ESP8266WiFi/src/WiFiServer.cpp b/libraries/ESP8266WiFi/src/WiFiServer.cpp
index 2b9adcc61..eb222c965 100644
--- a/libraries/ESP8266WiFi/src/WiFiServer.cpp
+++ b/libraries/ESP8266WiFi/src/WiFiServer.cpp
@@ -19,6 +19,11 @@
 
 #define LWIP_INTERNAL
 
+extern "C" {
+    #include "osapi.h"
+    #include "ets_sys.h"
+}
+
 #include "debug.h"
 #include "ESP8266WiFi.h"
 #include "WiFiClient.h"
diff --git a/libraries/Wire/utility/i2c.cpp b/libraries/Wire/utility/i2c.cpp
index e2ce0bb18..dc2e54902 100644
--- a/libraries/Wire/utility/i2c.cpp
+++ b/libraries/Wire/utility/i2c.cpp
@@ -5,9 +5,7 @@ extern "C" {
 #include "ets_sys.h"
 #include "osapi.h"
 #include "gpio.h"
-
-size_t ets_printf(const char*, ...);
-#define DEBUGV ets_printf
+#include "debug.h"
 }
 
 static uint8_t s_sda_pin = 0;