diff --git a/src/json_test.c b/src/json_test.c
index 1a1fdcb..74463f3 100644
--- a/src/json_test.c
+++ b/src/json_test.c
@@ -181,7 +181,7 @@
     reader.js_buf = (char_u *)" \"foo";
     reader.js_end = reader.js_buf + STRLEN(reader.js_buf);
     reader.js_cookie =        " \"foobar\"  ";
-    assert(json_decode_string(&reader, NULL) == OK);
+    assert(json_decode_string(&reader, NULL, '"') == OK);
 }
 #endif