diff --git a/RELEASES.md b/RELEASES.md
index aae25ab9988e9..83c44774da283 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -121,6 +121,12 @@ Stabilized APIs
 - [`i64::from_be_bytes`]
 - [`i64::from_le_bytes`]
 - [`i64::from_ne_bytes`]
+- [`i128::to_be_bytes`]
+- [`i128::to_le_bytes`]
+- [`i128::to_ne_bytes`]
+- [`i128::from_be_bytes`]
+- [`i128::from_le_bytes`]
+- [`i128::from_ne_bytes`]
 - [`isize::to_be_bytes`]
 - [`isize::to_le_bytes`]
 - [`isize::to_ne_bytes`]
@@ -151,6 +157,12 @@ Stabilized APIs
 - [`u64::from_be_bytes`]
 - [`u64::from_le_bytes`]
 - [`u64::from_ne_bytes`]
+- [`u128::to_be_bytes`]
+- [`u128::to_le_bytes`]
+- [`u128::to_ne_bytes`]
+- [`u128::from_be_bytes`]
+- [`u128::from_le_bytes`]
+- [`u128::from_ne_bytes`]
 - [`usize::to_be_bytes`]
 - [`usize::to_le_bytes`]
 - [`usize::to_ne_bytes`]
@@ -208,6 +220,12 @@ Compatibility Notes
 [`UnsafeCell::get`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html#method.get
 [`slice::as_ptr`]: https://doc.rust-lang.org/std/primitive.slice.html#method.as_ptr
 [`char::is_ascii`]: https://doc.rust-lang.org/std/primitive.char.html#method.is_ascii
+[`i128::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_be_bytes
+[`i128::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_le_bytes
+[`i128::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.from_ne_bytes
+[`i128::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_be_bytes
+[`i128::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_le_bytes
+[`i128::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i128.html#method.to_ne_bytes
 [`i16::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_be_bytes
 [`i16::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_le_bytes
 [`i16::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.i16.html#method.from_ne_bytes
@@ -240,6 +258,12 @@ Compatibility Notes
 [`isize::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.isize.html#method.to_ne_bytes
 [`iter::empty`]: https://doc.rust-lang.org/std/iter/fn.empty.html
 [`str::as_ptr`]: https://doc.rust-lang.org/std/primitive.str.html#method.as_ptr
+[`u128::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_be_bytes
+[`u128::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_le_bytes
+[`u128::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.from_ne_bytes
+[`u128::to_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_be_bytes
+[`u128::to_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_le_bytes
+[`u128::to_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u128.html#method.to_ne_bytes
 [`u16::from_be_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_be_bytes
 [`u16::from_le_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_le_bytes
 [`u16::from_ne_bytes`]: https://doc.rust-lang.org/stable/std/primitive.u16.html#method.from_ne_bytes