diff --git a/nixos/modules/deployment.nix b/nixos/modules/deployment.nix
index 22f56c7b01e242c6592d1ad8a8685fcf9549f2b6..f05aa1114cf3a5b2c8c30c1d70212bfd25d23ae3 100755
--- a/nixos/modules/deployment.nix
+++ b/nixos/modules/deployment.nix
@@ -44,6 +44,13 @@ in {
       ];
     };
 
+    # Raise the hard-limit on the size of $XDG_RUNTIME_DIR (ie
+    # /run/user/<uid>).  The default of 10% is too small on some systems for
+    # the temporary state morph creates to do the self-update.
+    services.logind.extraConfig = ''
+      RuntimeDirectorySize=50%
+    '';
+
     # Configure the deployment user.
     users.users.deployment = {
       # Without some shell no login is possible at all, even to execute our