diff --git a/t/test-lib.sh b/t/test-lib.sh
index b25249ec4..d303e6c94 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -26,6 +26,10 @@ then
 	# outside of t/, e.g. for running tests on the test library
 	# itself.
 	TEST_DIRECTORY=$(pwd)
+else
+	# ensure that TEST_DIRECTORY is an absolute path so that it
+	# is valid even if the current working directory is changed
+	TEST_DIRECTORY=$(cd "$TEST_DIRECTORY" && pwd) || exit 1
 fi
 if test -z "$TEST_OUTPUT_DIRECTORY"
 then