diff --git a/versioning.mk b/versioning.mk
index 4825c4e72..b336a7999 100644
--- a/versioning.mk
+++ b/versioning.mk
@@ -1,9 +1,9 @@
 MUTABLE_VERSION ?= canary
 
-GIT_COMMIT := $(shell git rev-parse HEAD)
-GIT_SHA := $(shell git rev-parse --short HEAD)
-GIT_TAG := $(shell git describe --tags --abbrev=0 2>/dev/null)
-GIT_DIRTY = $(shell test -n "`git status --porcelain`" && echo "dirty" || echo "clean")
+GIT_COMMIT ?= $(shell git rev-parse HEAD)
+GIT_SHA ?= $(shell git rev-parse --short HEAD)
+GIT_TAG ?= $(shell git describe --tags --abbrev=0 2>/dev/null)
+GIT_DIRTY ?= $(shell test -n "`git status --porcelain`" && echo "dirty" || echo "clean")
 
 ifdef VERSION
 	DOCKER_VERSION = $(VERSION)