diff --git a/images/nginx-slim/Makefile b/images/nginx-slim/Makefile
index 0bcce6696..0a5430822 100644
--- a/images/nginx-slim/Makefile
+++ b/images/nginx-slim/Makefile
@@ -13,8 +13,8 @@
 # limitations under the License.
 
 # 0.0.0 shouldn't clobber any released builds
-TAG = 0.25
-REGISTRY = gcr.io/google_containers
+TAG ?= 0.25
+REGISTRY ?= gcr.io/google_containers
 ARCH ?= $(shell go env GOARCH)
 ALL_ARCH = amd64 arm arm64 ppc64le