diff --git a/pkgs/by-name/gi/git-branchless/fix-esl01-indexedlog-for-rust-1_89.patch b/pkgs/by-name/gi/git-branchless/fix-esl01-indexedlog-for-rust-1_89.patch
new file mode 100644
index 000000000000..c5b03dc82d3d
--- /dev/null
+++ b/pkgs/by-name/gi/git-branchless/fix-esl01-indexedlog-for-rust-1_89.patch
@@ -0,0 +1,18 @@
+diff --git a/src/lock.rs b/src/lock.rs
+--- a/src/lock.rs
++++ b/src/lock.rs
+@@ -132,10 +132,10 @@ impl ScopedDirLock {
+ 
+         // Lock
+         match (opts.exclusive, opts.non_blocking) {
+-            (true, false) => file.lock_exclusive(),
+-            (true, true) => file.try_lock_exclusive(),
+-            (false, false) => file.lock_shared(),
+-            (false, true) => file.try_lock_shared(),
++            (true, false) => fs2::FileExt::lock_exclusive(&file),
++            (true, true) => fs2::FileExt::try_lock_exclusive(&file),
++            (false, false) => fs2::FileExt::lock_shared(&file),
++            (false, true) => fs2::FileExt::try_lock_shared(&file),
+         }
+         .context(&path, || {
+             format!(
diff --git a/pkgs/by-name/gi/git-branchless/package.nix b/pkgs/by-name/gi/git-branchless/package.nix
index 2355d30ee5dd..6e7946dd45f3 100644
--- a/pkgs/by-name/gi/git-branchless/package.nix
+++ b/pkgs/by-name/gi/git-branchless/package.nix
@@ -21,6 +21,20 @@ rustPlatform.buildRustPackage rec {
     hash = "sha256-8uv+sZRr06K42hmxgjrKk6FDEngUhN/9epixRYKwE3U=";
   };
 
+  # Patch the vendored esl01-indexedlog crate.
+  # This is necessary to fix the build for rust 1.89. See:
+  # - https://github.com/NixOS/nixpkgs/issues/437051
+  # - https://github.com/arxanas/git-branchless/issues/1585
+  # - https://github.com/facebook/sapling/issues/1119
+  # The patch is derived from:
+  # - https://github.com/facebook/sapling/commit/9e27acb84605079bf4e305afb637a4d6801831ac
+  postPatch = ''
+    (
+      cd ../git-branchless-*-vendor/esl01-indexedlog-*/
+      patch -p1 < ${./fix-esl01-indexedlog-for-rust-1_89.patch}
+    )
+  '';
+
   cargoHash = "sha256-i7KpTd4fX3PrhDjj3R9u98rdI0uHkpQCxSmEF+Gu7yk=";
 
   nativeBuildInputs = [ pkg-config ];