diff --git a/Makefile b/Makefile
index ca85c7adf4d896d01136e9536ae25795a1174afd..9ca933445c2668987c6aa7bc34117e0f70f47fbd 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-CFLAGS += -Wall -Werror
+CFLAGS += -std=c99 -Wall -Werror
 
 # find our hammer build - adjust this to your needs
 # i have, for instance, symlinks: