diff --git a/sink/Makefile b/sink/Makefile
index 13d7d45..ab8bdbd 100644
--- a/sink/Makefile
+++ b/sink/Makefile
@@ -8,7 +8,7 @@ C_INCLUDES = \
 -I../cube/User/Inc
 
 CC = gcc
-CFLAGS = $(C_INCLUDES) -Wall -Werror
+CFLAGS = $(C_INCLUDES) -Wall -Werror -std=c99
 LDFLAGS =
 TARGET = sink20169
 
@@ -28,4 +28,4 @@ $(BUILD_DIR):
 
 .phony: clean
 clean:
-	-rm -rf $(BUILD_DIR)
\ No newline at end of file
+	-rm -rf $(BUILD_DIR)