diff --git a/pkgs/development/php-packages/composer/default.nix b/pkgs/development/php-packages/composer/default.nix
index d9d431aeccc..fd26cc0e484 100644
--- a/pkgs/development/php-packages/composer/default.nix
+++ b/pkgs/development/php-packages/composer/default.nix
@@ -1,4 +1,4 @@
-{ lib, callPackage, fetchFromGitHub, php, unzip, _7zz, xz, git, curl, cacert, makeBinaryWrapper }:
+{ lib, callPackage, fetchgit, php, unzip, _7zz, xz, git, curl, cacert, makeBinaryWrapper }:
 
 php.buildComposerProject (finalAttrs: {
   composer = callPackage ../../../build-support/php/pkgs/composer-phar.nix { };
@@ -6,11 +6,14 @@ php.buildComposerProject (finalAttrs: {
   pname = "composer";
   version = "2.6.4";
 
-  src = fetchFromGitHub {
-    owner = "composer";
-    repo = "composer";
+
+  # We use `fetchgit` instead of `fetchFromGitHub` to ensure the existence
+  # of the `composer.lock` file, which is omitted in the archive downloaded
+  # via `fetchFromGitHub`.
+  src = fetchgit {
+    url = "https://github.com/composer/composer.git";
     rev = finalAttrs.version;
-    hash = "sha256-o7z2GBiYjTwDQR9ZFuOOV8zsKUuGqyA52dvwTzo4hVA=";
+    hash = "sha256-8lylMfTARff+gBZpIRqttmE0jeXdJnLHZKVmqHY3p+s=";
   };
 
   nativeBuildInputs = [ makeBinaryWrapper ];
@@ -20,7 +23,7 @@ php.buildComposerProject (finalAttrs: {
       --prefix PATH : ${lib.makeBinPath [ _7zz cacert curl git unzip xz ]}
   '';
 
-  vendorHash = "sha256-S6LprixkLIbD+qqvg+eYjWsDe+jFl9NO1qWztWYKPXs=";
+  vendorHash = "sha256-SG5RsKaP7zqJY2vjvULuNdf7w6tAGh7/dlxx2Pkfj2A=";
 
   meta = {
     changelog = "https://github.com/composer/composer/releases/tag/${finalAttrs.version}";