diff --git a/src/modules/ExternalNotificationModule.cpp b/src/modules/ExternalNotificationModule.cpp
index 90fbf28f0..56a0db941 100644
--- a/src/modules/ExternalNotificationModule.cpp
+++ b/src/modules/ExternalNotificationModule.cpp
@@ -49,7 +49,11 @@
 */
 
 // Default configurations
+#ifdef EXT_NOTIFY_OUT
 #define EXT_NOTIFICATION_MODULE_OUTPUT EXT_NOTIFY_OUT
+#else
+#define EXT_NOTIFICATION_MODULE_OUTPUT 0
+#endif
 #define EXT_NOTIFICATION_MODULE_OUTPUT_MS 1000
 
 #define ASCII_BELL 0x07