3 files changed, 13 insertions, 0 deletions
diff --git a/t/t2104-update-index-skip-worktree.sh b/t/t2104-update-index-skip-worktree.sh
index 1d0879be0..29c1fb10c 100755
--- a/t/t2104-update-index-skip-worktree.sh
+++ b/t/t2104-update-index-skip-worktree.sh
@@ -7,6 +7,8 @@ test_description='skip-worktree bit test'
 
 . ./test-lib.sh
 
+test_set_index_version 3
+
 cat >expect.full <<EOF
 H 1
 H 2
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index aeae3ca76..0bf1e63ab 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -32,6 +32,11 @@ test_set_editor () {
 	export EDITOR
 }
 
+test_set_index_version () {
+    GIT_INDEX_VERSION="$1"
+    export GIT_INDEX_VERSION
+}
+
 test_decode_color () {
 	awk '
 		function name(n) {
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 1531c241c..569b52dc0 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -108,6 +108,12 @@ export GIT_AUTHOR_EMAIL GIT_AUTHOR_NAME
 export GIT_COMMITTER_EMAIL GIT_COMMITTER_NAME
 export EDITOR
 
+if test -n "${TEST_GIT_INDEX_VERSION:+isset}"
+then
+	GIT_INDEX_VERSION="$TEST_GIT_INDEX_VERSION"
+	export GIT_INDEX_VERSION
+fi
+
 # Add libc MALLOC and MALLOC_PERTURB test
 # only if we are not executing the test with valgrind
 if expr " $GIT_TEST_OPTS " : ".* --valgrind " >/dev/null ||