diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index 3230a08c27630..8db1fd92530d3 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -157,7 +157,7 @@ declare_lint! {
 
 declare_lint! {
     pub TRANSMUTE_FROM_FN_ITEM_TYPES,
-    Warn,
+    Deny,
     "transmute from function item type to pointer-sized type erroneously allowed"
 }