diff --git a/Makefile b/Makefile
index 47b3d6d..d227ce1 100644
--- a/Makefile
+++ b/Makefile
@@ -53,7 +53,7 @@ ifeq ($(I),lang)
 	node tools/build-lang-image.js --lang $(L)
 else ifeq ($(I),ubuntu)
 	docker pull ubuntu:rolling
-	hash="$$(docker inspect ubuntu:rolling | jq '.[0].Id' -r | sha1sum | awk '{ print $$1 }')"; echo "FROM ubuntu:rolling" | docker build --label riju.image-hash="$${hash}" -t riju:$(I) -
+	hash="$$(docker inspect ubuntu:rolling -f '{{ .Id }}' | sha1sum | awk '{ print $$1 }')"; echo "FROM ubuntu:rolling" | docker build --label riju.image-hash="$${hash}" -t riju:$(I) -
 else ifneq (,$(filter $(I),admin ci))
 	docker build . -f docker/$(I)/Dockerfile -t riju:$(I) $(NO_CACHE)
 else
@@ -81,7 +81,7 @@ else
 LANG_TAG := $(I)
 endif
 
-IMAGE_HASH := "$$(docker inspect riju:$(LANG_TAG) | jq '.[0].Config.Labels["riju.image-hash"]' -r)"
+IMAGE_HASH := "$$(docker inspect riju:$(LANG_TAG) -f '{{ index .Config.Labels "riju.image-hash" }}')"
 WITH_IMAGE_HASH := -e RIJU_IMAGE_HASH=$(IMAGE_HASH)
 
 shell: # I=<shell> [L=<lang>] [E[E]=1] [P1|P2=<port>] [CMD="<arg>..."] : Launch Docker image with shell