diff --git a/modules/home/yubikey.nix b/modules/home/yubikey.nix
index 5bb2f8b..26b5d19 100644
--- a/modules/home/yubikey.nix
+++ b/modules/home/yubikey.nix
@@ -37,7 +37,7 @@
       '';
     };
     home.sessionVariables = {
-      SSH_AUTH_SOCK = "$XDG_RUNTIME_DIR/gnupg/S.gpg-agent.ssh";
+      SSH_AUTH_SOCK = "$\{XDG_RUNTIME_DIR\}/gnupg/S.gpg-agent.ssh";
     };
   };
 }