diff --git a/.gitignore b/.gitignore
index 4070854d..e27a6c43 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /.image.json
+/.image.tag
diff --git a/Makefile b/Makefile
index ef059cfc..0d672f33 100644
--- a/Makefile
+++ b/Makefile
@@ -6,9 +6,14 @@ TAG?=latest
 
 # Process images.json through the images-with-extras script
 IMAGE_JSON=.image.json
-.image.json: images.json .scripts/images-with-extras
+.image.json: images.json .scripts/images-with-extras .image.tag
 	< images.json jq '.[] | select(.tag == "$(TAG)") | [ . ]' | .scripts/images-with-extras | jq '.[]' > $@
 
+# Track TAG as a file so that .image.json regenerates when TAG changes
+.image.tag: FORCE
+	@echo '$(TAG)' | cmp -s - $@ || echo '$(TAG)' > $@
+FORCE:
+
 # Extract configuration from selected image
 XDR_REPO =          $(shell < $(IMAGE_JSON) jq -r '.deps[] | select(.name == "xdr") | .repo')
 XDR_SHA =           $(shell < $(IMAGE_JSON) jq -r '.deps[] | select(.name == "xdr") | .sha')