diff --git a/stm32f100/Makefile b/stm32f100/Makefile
index e1495330..e44c96a7 100755
--- a/stm32f100/Makefile
+++ b/stm32f100/Makefile
@@ -44,7 +44,7 @@ OCD	= sudo ~/openocd-git/openocd/src/openocd \
 
 # INCLUDES = -I$(SRCDIR) $(LIBINC)
 INCLUDES = $(LIBINC)
-CFLAGS  = $(CPU) $(CMSIS_OPT) $(OTHER_OPT) -Wall -fno-common -fno-strict-aliasing -O2 $(INCLUDES) -g -Wfatal-errors -g
+CFLAGS  = $(CPU) $(CMSIS_OPT) $(OTHER_OPT) -Wall -fno-common -fno-strict-aliasing -O2 $(INCLUDES) -g -Wfatal-errors -g -std=c99
 ASFLAGS = $(CFLAGS) -x assembler-with-cpp
 LDFLAGS = -Wl,--gc-sections,-Map=$*.map,-cref -T $(LDSCRIPT) $(CPU)
 ARFLAGS = cr