diff --git a/build.sh b/build.sh
index 05d916e..a341e49 100755
--- a/build.sh
+++ b/build.sh
@@ -4,7 +4,7 @@ set -euo pipefail
 
 source ./scripts/test_lib.sh
 
-GIT_SHA=$(git rev-parse --short HEAD || echo "GitNotFound")
+: ${GIT_SHA:=$(git rev-parse --short HEAD || echo "GitNotFound")}
 if [[ -n "${FAILPOINTS:-}" ]]; then
   GIT_SHA="$GIT_SHA"-FAILPOINTS
 fi