--- a/util-src/crand.c	Sat Dec 02 11:11:32 2017 +0100
+++ b/util-src/crand.c	Sun Dec 03 14:13:56 2017 +0100
@@ -91,7 +91,7 @@
 		return lua_error(L);
 	}
 
-	if(RAND_bytes(buf, len) != 1) {
+	if(RAND_bytes((unsigned char *)buf, len) != 1) {
 		/* TODO ERR_get_error() */
 		lua_pushstring(L, "RAND_bytes() failed");
 		return lua_error(L);