diff --git a/comanage-registry-base/Dockerfile b/comanage-registry-base/Dockerfile
index bbaed60..2bbc134 100644
--- a/comanage-registry-base/Dockerfile
+++ b/comanage-registry-base/Dockerfile
@@ -51,7 +51,8 @@ ARG COMANAGE_REGISTRY_VERSION
 ENV COMANAGE_REGISTRY_VERSION ${COMANAGE_REGISTRY_VERSION:-develop}
 LABEL comanage_registry_version=${COMANAGE_REGISTRY_VERSION}
 
-ENV COMANAGE_REGISTRY_SRC_URL=https://github.com/Internet2/comanage-registry/archive/${COMANAGE_REGISTRY_VERSION}.tar.gz
+ARG COMANAGE_REGISTRY_SRC_URL
+ENV COMANAGE_REGISTRY_SRC_URL=${COMANAGE_REGISTRY_SRC_URL:-https://github.com/Internet2/comanage-registry/archive/${COMANAGE_REGISTRY_VERSION}.tar.gz}
 
 ARG COMANAGE_REGISTRY_DIR
 ENV COMANAGE_REGISTRY_DIR ${COMANAGE_REGISTRY_DIR:-/srv/comanage-registry}