diff --git a/test/json.c b/test/json.c
index 5280745..1a172f4 100644
--- a/test/json.c
+++ b/test/json.c
@@ -88,7 +88,7 @@
 	return root;
 }
 
-const cn_cbor * ParseJson(char * fileName)
+const cn_cbor * ParseJson(const char * fileName)
 {
 	int     cch;
 	char	rgch[8 * 1024];