diff --git a/Cargo.toml b/Cargo.toml
index ffa457b..8b82ddb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,7 +32,7 @@ min_const_generics = [] # MSRV 1.51: support arrays via min_const_generics
 wasm_simd = []    # MSRV 1.54.0: support wasm simd types
 aarch64_simd = [] # MSRV 1.59.0: support aarch64 simd types
 
-must_cast = [] # MSRV 1.57.0: support the `must` module.
+must_cast = [] # MSRV 1.64.0: support the `must` module.
 
 const_zeroed = [] # MSRV 1.75.0: support const `zeroed()`
 
diff --git a/src/lib.rs b/src/lib.rs
index aa2812b..cafab3b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -123,6 +123,8 @@ macro_rules! transmute {
   ($val:expr) => {
     ::core::mem::transmute_copy(&::core::mem::ManuallyDrop::new($val))
   };
+  // This arm is for use in const contexts, where the borrow required to use transmute_copy poses an issue
+  // since the compiler hedges that the type being borrowed could have interior mutability.
   ($srcty:ty; $dstty:ty; $val:expr) => {
     {
       union Transmute<A, B> {