diff --git a/config.mk b/config.mk
index 8efca9a..ad629e6 100644
--- a/config.mk
+++ b/config.mk
@@ -28,7 +28,7 @@ LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS}
 # flags
 CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
 #CFLAGS   = -g -std=c99 -pedantic -Wall -O0 ${INCS} ${CPPFLAGS}
-CFLAGS   = -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os ${INCS} ${CPPFLAGS}
+CFLAGS   = -std=c99 -pedantic -Wall -Wextra -Werror -Wno-unused-parameter -Wno-sign-compare -Wno-deprecated-declarations -Os ${INCS} ${CPPFLAGS}
 LDFLAGS  = ${LIBS}
 
 # Solaris