diff --git a/Makefile b/Makefile
index e239aeb..3763dad 100644
--- a/Makefile
+++ b/Makefile
@@ -5,8 +5,8 @@ CONTAINER_RUNTIME?=$(shell which podman)
 
 # GIT_IMAGE_REGISTRY_NAME
 # Defines the name of the new container to be built using several variables.
-GIT_IMAGE_REGISTRY_NAME:=git.cryptic.systems
-GIT_IMAGE_REGISTRY_USER:=volker.raschek
+GIT_IMAGE_REGISTRY_NAME?=git.cryptic.systems
+GIT_IMAGE_REGISTRY_USER?=volker.raschek
 
 GIT_IMAGE_NAMESPACE?=${GIT_IMAGE_REGISTRY_USER}
 GIT_IMAGE_NAME:=git