diff --git a/pkgs/by-name/do/dovecot/package.nix b/pkgs/by-name/do/dovecot/package.nix
index 43773164c394..1dce4874455d 100644
--- a/pkgs/by-name/do/dovecot/package.nix
+++ b/pkgs/by-name/do/dovecot/package.nix
@@ -127,6 +127,12 @@ stdenv.mkDerivation rec {
       url = "https://salsa.debian.org/debian/dovecot/-/raw/debian/1%252.3.19.1+dfsg1-2/debian/patches/Support-openssl-3.0.patch";
       hash = "sha256-PbBB1jIY3jIC8Js1NY93zkV0gISGUq7Nc67Ul5tN7sw=";
     })
+    # Fix build with gcc15
+    (fetchpatch {
+      name = "dovecot-test-data-stack-drop-bogus-assertion.patch";
+      url = "https://github.com/dovecot/core/commit/9f642dd868db6e7401f24e4fb4031b5bdca8aae7.patch";
+      hash = "sha256-dAX80dRqOba9Fkzl11ChYJ6vqcgfkaw/o+TOQKCnnns=";
+    })
   ]
   ++ lib.optionals stdenv.hostPlatform.isDarwin [
     # fix timespec calls