diff --git a/lib/resource.c b/lib/resource.c
index 2a1ad62b..1b915073 100644
--- a/lib/resource.c
+++ b/lib/resource.c
@@ -253,7 +253,7 @@ struct mblock {
   byte data[0];
 };
 
-static void mbl_free(resource *r)
+static void mbl_free(resource *r UNUSED)
 {
 }