diff --git a/tests/docker/Makefile.include b/tests/docker/Makefile.include
index 78af46837b0e2a2781e54cf352216f4a723f5b6f..4f4707dae03344080d08bf7dec41a8a33eadb3e9 100644
--- a/tests/docker/Makefile.include
+++ b/tests/docker/Makefile.include
@@ -107,9 +107,8 @@ docker-run-%: docker-qemu-src
 	fi
 	$(if $(filter $(TESTS),$(CMD)),$(if $(filter $(IMAGES),$(IMAGE)), \
 		$(call quiet-command,\
-			if $(SRC_PATH)/tests/docker/docker.py images \
-				--format={{.Repository}}:{{.Tag}} | \
-					grep -qx qemu:$(IMAGE); then \
+			if $(SRC_PATH)/tests/docker/docker.py images | \
+				awk '$$1=="qemu" && $$2=="$(IMAGE)"{found=1} END{exit(!found)}'; then \
 				$(SRC_PATH)/tests/docker/docker.py run $(if $V,,--rm) \
 				-t \
 				$(if $(DEBUG),-i,--net=none) \
diff --git a/tests/docker/common.rc b/tests/docker/common.rc
index 77069e12856a21fe8d0b67108368ae01e6f549f4..0c6d8d5ecea61229aa40c9d431ec8300aade96d5 100755
--- a/tests/docker/common.rc
+++ b/tests/docker/common.rc
@@ -24,6 +24,7 @@ requires()
 build_qemu()
 {
     $QEMU_SRC/configure \
+        --enable-werror \
         ${TARGET_LIST:+"--target-list=${TARGET_LIST}"} \
         --prefix="$PWD/install" \
         $EXTRA_CONFIGURE_OPTS \