diff --git a/pkgs/by-name/tn/tnef/package.nix b/pkgs/by-name/tn/tnef/package.nix
index e8322268836c..f80c31aec274 100644
--- a/pkgs/by-name/tn/tnef/package.nix
+++ b/pkgs/by-name/tn/tnef/package.nix
@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchFromGitHub,
+  fetchpatch,
   autoreconfHook,
 }:
 
@@ -16,6 +17,15 @@ stdenv.mkDerivation rec {
     sha256 = "104g48mcm00bgiyzas2vf86331w7bnw7h3bc11ib4lp7rz6zqfck";
   };
 
+  patches = [
+    # Fix gcc-15 build failure: https://github.com/verdammelt/tnef/pull/49
+    (fetchpatch {
+      name = "gcc-15.patch";
+      url = "https://github.com/verdammelt/tnef/commit/86bfa75cfacbe71c8d5282fa0065981b4544c5ad.patch";
+      hash = "sha256-iWQop57riqwDLVi5Ba5s4f34lGXgvKO3ZMTgWbAoRIY=";
+    })
+  ];
+
   doCheck = true;
 
   nativeBuildInputs = [ autoreconfHook ];