diff --git a/pkgs/tools/networking/mu/default.nix b/pkgs/tools/networking/mu/default.nix
index bbaa588545f6..91321cb593f6 100644
--- a/pkgs/tools/networking/mu/default.nix
+++ b/pkgs/tools/networking/mu/default.nix
@@ -14,20 +14,20 @@
 
 stdenv.mkDerivation rec {
   pname = "mu";
-  version = "1.8.8";
+  version = "1.8.9";
 
   src = fetchFromGitHub {
     owner = "djcb";
     repo = "mu";
     rev = "v${version}";
-    hash = "sha256-kgskeQM6zESkjDWmgGqhZlGnH8naZ5k0sw+70ZzW2/E=";
+    hash = "sha256-AqbTYcPwV9iNar34pESbz9Vp/88hhB+/VxcLIhLZ16o=";
   };
 
   postPatch = ''
     # Fix mu4e-builddir (set it to $out)
     substituteInPlace mu4e/mu4e-config.el.in \
       --replace "@abs_top_builddir@" "$out"
-    substituteInPlace lib/utils/mu-utils.cc \
+    substituteInPlace lib/utils/mu-test-utils.cc \
       --replace "/bin/rm" "${coreutils}/bin/rm"
   '';