diff --git a/t/test-lib.sh b/t/test-lib.sh
index 32112a4..19bd8c1 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -22,10 +22,12 @@ test_set_prereq() {
 }
 satisfied_prereq=" "
 
-if [[ $(uname -s) = MSYS* ]] || [[ $(uname -s) = MINGW* ]]; then
+case "$(uname -s)" in
+MSYS*|MINGW*)
 	test_set_prereq WIN
 	export TEST_CMP='diff --strip-trailing-cr -u'
-fi
+	;;
+esac
 
 test_cmp() {
 	${TEST_CMP:-diff -u} "$@"