diff --git a/pkgs/tools/security/onlykey-agent/default.nix b/pkgs/tools/security/onlykey-agent/default.nix
index 36a1cb284759..f37073d602da 100644
--- a/pkgs/tools/security/onlykey-agent/default.nix
+++ b/pkgs/tools/security/onlykey-agent/default.nix
@@ -26,6 +26,7 @@ let
     propagatedBuildInputs = oa.propagatedBuildInputs or [ ] ++ [
       bech32
       cryptography
+      cython
       docutils
       pycryptodome
       pynacl