diff --git a/t/test-lib.sh b/t/test-lib.sh
index 713eb718e6..1f36188685 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -51,7 +51,7 @@ export LSAN_OPTIONS
 
 ################################################################
 # It appears that people try to run tests without building...
-"$GIT_BUILD_DIR/git" >/dev/null
+test -n "$GIT_TEST_INSTALLED" || "$GIT_BUILD_DIR/git" >/dev/null ||
 if test $? != 1
 then
 	echo >&2 'error: you do not seem to have built git yet.'