diff --git a/test/test-lib.sh b/test/test-lib.sh
index d7282ff6..9dcb2d2e 100644
--- a/test/test-lib.sh
+++ b/test/test-lib.sh
@@ -557,7 +557,7 @@ test_declare_external_prereq () {
 	test_missing_external_prereq_${binary}_=t
 $binary () {
 	echo -n \"\$test_subtest_missing_external_prereqs_\" | grep -e \" $name \" ||
-	test_subtest_missing_external_prereqs_=\"$test_subtest_missing_external_prereqs_ $name\"
+	test_subtest_missing_external_prereqs_=\"\$test_subtest_missing_external_prereqs_ $name\"
 	false
 }"
 }