diff --git a/qrexec-lib/Makefile b/qrexec-lib/Makefile
index b18296f..1b34c48 100644
--- a/qrexec-lib/Makefile
+++ b/qrexec-lib/Makefile
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS+=-I. -g -Wall -Wextra -pie -fPIC `pkg-config --cflags vchan-$(BACKEND_VMM)`
+CFLAGS+=-I. -g -Wall -Wextra -Werror -pie -fPIC `pkg-config --cflags vchan-$(BACKEND_VMM)`
 COMMONIOALL=ioall.o
 SO_VER=1
 LDFLAGS=-shared