diff --git a/mongoose.c b/mongoose.c
index 5caa099e..fbc85dce 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -15309,7 +15309,8 @@ void mg_lwip_if_add_conn(struct mg_connection *nc);
 void mg_lwip_if_remove_conn(struct mg_connection *nc);
 time_t mg_lwip_if_poll(struct mg_iface *iface, int timeout_ms);
 
-#if defined(RTOS_SDK) || defined(ESP_PLATFORM)
+// If compiling for Mongoose OS.
+#ifdef MGOS_HAVE_CORE
 extern void mgos_lock();
 extern void mgos_unlock();
 #else
diff --git a/src/common/platforms/lwip/mg_lwip_net_if.c b/src/common/platforms/lwip/mg_lwip_net_if.c
index 91b69bb9..42aa1e3b 100644
--- a/src/common/platforms/lwip/mg_lwip_net_if.c
+++ b/src/common/platforms/lwip/mg_lwip_net_if.c
@@ -102,7 +102,8 @@ void mg_lwip_if_add_conn(struct mg_connection *nc);
 void mg_lwip_if_remove_conn(struct mg_connection *nc);
 time_t mg_lwip_if_poll(struct mg_iface *iface, int timeout_ms);
 
-#if defined(RTOS_SDK) || defined(ESP_PLATFORM)
+// If compiling for Mongoose OS.
+#ifdef MGOS_HAVE_CORE
 extern void mgos_lock();
 extern void mgos_unlock();
 #else