diff --git a/version.sh b/version.sh
index 2b0ea3f..651cff5 100755
--- a/version.sh
+++ b/version.sh
@@ -1,12 +1,15 @@
 #!/bin/sh
 
-[ -z "${VERSION}" ] && VERSION="$(git describe --tags --match='v[0-9].*' 2>/dev/null)" \
-                    && VERSION="${VERSION#v}"
+export GIT_DIR=.git
+export GIT_WORK_TREE=.
 
-[ -z "${VERSION}" ] && VERSION="$(git rev-parse HEAD 2>/dev/null)"
+[ -z "$VERSION" ] && VERSION="$(git describe --tags --match='v[0-9].*' 2>/dev/null)" \
+                  && VERSION="${VERSION#v}"
 
-[ -z "${VERSION}" ] && VERSION="$(cat VERSION 2>/dev/null)"
+[ -z "$VERSION" ] && VERSION="$(git rev-parse HEAD 2>/dev/null)"
 
-[ -z "${VERSION}" ] && VERSION="0.0.0"
+[ -z "$VERSION" ] && VERSION="$(cat VERSION 2>/dev/null)"
 
-printf "%s" "${VERSION}" | tee VERSION
+[ -z "$VERSION" ] && VERSION="0.0.0"
+
+printf "%s" "$VERSION" | tee VERSION