diff --git a/pkgs/development/python-modules/consonance/default.nix b/pkgs/development/python-modules/consonance/default.nix
index b14d965e5629..e13665cd5dc3 100644
--- a/pkgs/development/python-modules/consonance/default.nix
+++ b/pkgs/development/python-modules/consonance/default.nix
@@ -1,6 +1,7 @@
 { lib
 , buildPythonPackage
 , fetchFromGitHub
+, fetchpatch
 , dissononce
 , python-axolotl-curve25519
 , transitions
@@ -23,6 +24,15 @@ buildPythonPackage rec {
     hash = "sha256-BhgxLxjKZ4dSL7DqkaoS+wBPCd1SYZomRKrtDLdGmYQ=";
   };
 
+  patches = [
+    # https://github.com/tgalal/consonance/pull/9
+    (fetchpatch {
+      name = "fix-type-error.patch";
+      url = "https://github.com/tgalal/consonance/pull/9/commits/92fb78af98a18f0533ec8a286136968174fb0baf.patch";
+      hash = "sha256-wVUGxZ4W2zPyrcQPQTc85LcRUtsLbTBVzS10NEolpQY=";
+    })
+  ];
+
   propagatedBuildInputs = [
     dissononce
     python-axolotl-curve25519