diff --git a/pkgs/development/python-modules/ircstates/default.nix b/pkgs/development/python-modules/ircstates/default.nix
index 61065d492f9a..c6e8f06dea30 100644
--- a/pkgs/development/python-modules/ircstates/default.nix
+++ b/pkgs/development/python-modules/ircstates/default.nix
@@ -23,6 +23,8 @@ buildPythonPackage rec {
 
   build-system = [ setuptools ];
 
+  pythonRelaxDeps = [ "pendulum" ];
+
   dependencies = [
     irctokens
     pendulum