diff --git a/Makefile b/Makefile
index 9053626291..36538b041d 100644
--- a/Makefile
+++ b/Makefile
@@ -9,7 +9,7 @@ VERSION = 0.92
 
 BUNDLE = Factor.app
 LIBPATH = -L/usr/X11R6/lib
-CFLAGS = -Wall
+CFLAGS = -Wall -Werror
 FFI_TEST_CFLAGS = -fPIC
 
 ifdef DEBUG