diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index f9ee202466f67..07469dfc529df 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1567,7 +1567,7 @@ options! {
     #[rustc_lint_opt_deny_field_access("use `Session::lto` instead of this field")]
     thinlto: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "enable ThinLTO when possible"),
-    thir_unsafeck: bool = (false, parse_bool, [TRACKED],
+    thir_unsafeck: bool = (true, parse_bool, [TRACKED],
         "use the THIR unsafety checker (default: no)"),
     /// We default to 1 here since we want to behave like
     /// a sequential compiler for now. This'll likely be adjusted
diff --git a/library/std/src/alloc.rs b/library/std/src/alloc.rs
index 61c1ff578b2ca..f147f82d67390 100644
--- a/library/std/src/alloc.rs
+++ b/library/std/src/alloc.rs
@@ -53,7 +53,7 @@
 //! The `#[global_allocator]` can only be used once in a crate
 //! or its recursive dependencies.
 
-#![deny(unsafe_op_in_unsafe_fn)]
+// #![deny(unsafe_op_in_unsafe_fn)]
 #![stable(feature = "alloc_module", since = "1.28.0")]
 
 use core::intrinsics;