diff --git a/mongoose.h b/mongoose.h
index 43cfe12e..584e3e11 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -603,10 +603,6 @@ typedef struct stat cs_stat_t;
 #define __cdecl
 #define _FILE_OFFSET_BITS 32
 
-#if !defined(RTOS_SDK) && !defined(__cplusplus)
-#define fileno(x) -1
-#endif
-
 #define MG_LWIP 1
 
 /* struct timeval is defined in sys/time.h. */
diff --git a/src/common/platforms/esp8266/common.mk b/src/common/platforms/esp8266/common.mk
index 53452215..5efc4b9a 100644
--- a/src/common/platforms/esp8266/common.mk
+++ b/src/common/platforms/esp8266/common.mk
@@ -68,7 +68,7 @@ C_CXX_FLAGS  = -W -Wall -Werror -Wundef -Wno-comment -Wno-variadic-macros -Wpoin
                -DCS_PLATFORM=3 \
                -ffunction-sections -fdata-sections
 
-CFLAGS = -std=c99 $(C_CXX_FLAGS)
+CFLAGS = -std=gnu99 $(C_CXX_FLAGS)
 CXXFLAGS = -std=gnu++11 -fno-exceptions $(C_CXX_FLAGS)
 
 # linker flags used to generate the main object file
diff --git a/src/common/platforms/platform_esp8266.h b/src/common/platforms/platform_esp8266.h
index 0428f058..3bef0441 100644
--- a/src/common/platforms/platform_esp8266.h
+++ b/src/common/platforms/platform_esp8266.h
@@ -42,10 +42,6 @@ typedef struct stat cs_stat_t;
 #define __cdecl
 #define _FILE_OFFSET_BITS 32
 
-#if !defined(RTOS_SDK) && !defined(__cplusplus)
-#define fileno(x) -1
-#endif
-
 #define MG_LWIP 1
 
 /* struct timeval is defined in sys/time.h. */