diff --git a/qmemman/Makefile b/qmemman/Makefile
index 2c1da6a..59e485a 100644
--- a/qmemman/Makefile
+++ b/qmemman/Makefile
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS=-Wall -g -O3
+CFLAGS=-Wall -Wextra -Werror -g -O3
 all:	meminfo-writer
 meminfo-writer: meminfo-writer.o
 	$(CC) -g -o meminfo-writer meminfo-writer.o -lxenstore
diff --git a/qrexec-lib/Makefile b/qrexec-lib/Makefile
index ea840ea..9130b4b 100644
--- a/qrexec-lib/Makefile
+++ b/qrexec-lib/Makefile
@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS+=-I. -g -Wall -pie -fPIC -Wextra
+CFLAGS+=-I. -g -Wall -Wextra -Werror -pie -fPIC
 XENLIBS=-lxenctrl -lxenstore -lvchan
 COMMONIOALL=ioall.o
 SO_VER=1