diff --git a/examples/ESP8266_RTOS/Makefile b/examples/ESP8266_RTOS/Makefile
index 2d0b16a451f473259d4229593bdaab3db71957fc..05752a442c3fec313156d6cb819636d10f03749d 100644
--- a/examples/ESP8266_RTOS/Makefile
+++ b/examples/ESP8266_RTOS/Makefile
@@ -15,7 +15,7 @@ TARGET = eagle
 #FLAVOR = release
 FLAVOR = debug
 
-EXTRA_CCFLAGS += -Wall -Werror
+EXTRA_CCFLAGS += -Wall -Werror -DRTOS_SDK
 
 ifndef PDIR # {
 GEN_IMAGES= eagle.app.v6.out
diff --git a/mongoose.h b/mongoose.h
index 405905ae11addf814a242e9519398d1b2c9beca4..e1dd584eb5bc4e7492a671207a28a9bfaeb820de 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -475,7 +475,10 @@ typedef struct stat cs_stat_t;
 #define INT64_X_FMT PRIx64
 #define __cdecl
 #define _FILE_OFFSET_BITS 32
-#define fineno(x) -1
+
+#ifndef RTOS_SDK
+#define fileno(x) -1
+#endif
 
 #define MG_LWIP 1