1 files changed, 3 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index 26f75b8..2d2eedf 100644
--- a/Makefile
+++ b/Makefile
@@ -7,6 +7,8 @@ INCLUDE_FLAGS := $(shell pkg-config --cflags libsystemd)
 VERSION := $(shell $(PYTHON) setup.py --version)
 TESTFLAGS = -v
 
+CFLAGS = -std=c99
+
 define buildscript
 import sys,sysconfig
 print("build/lib.{}-{}.{}".format(sysconfig.get_platform(), *sys.version_info[:2]))
@@ -31,7 +33,7 @@ update-constants: update-constants.py $(INCLUDE_DIR)/systemd/sd-messages.h
 	mv docs/id128.rst{.tmp,}
 
 build:
-	$(PYTHON) setup.py build_ext $(INCLUDE_FLAGS)
+	CFLAGS=$(CFLAGS) $(PYTHON) setup.py build_ext $(INCLUDE_FLAGS)
 	$(PYTHON) setup.py build
 
 install: