diff --git a/nixos/modules/services/matrix/mautrix-telegram.nix b/nixos/modules/services/matrix/mautrix-telegram.nix
index cbca6435d6c2..fc8b95051ddb 100644
--- a/nixos/modules/services/matrix/mautrix-telegram.nix
+++ b/nixos/modules/services/matrix/mautrix-telegram.nix
@@ -128,6 +128,18 @@ in {
       after = [ "network-online.target" ] ++ cfg.serviceDependencies;
       path = [ pkgs.lottieconverter ];
 
+      # mautrix-telegram tries to generate a dotfile in the home directory of
+      # the running user if using a postgresql databse:
+      #
+      #  File "python3.10/site-packages/asyncpg/connect_utils.py", line 257, in _dot_postgre>
+      #    return (pathlib.Path.home() / '.postgresql' / filename).resolve()
+      #  File "python3.10/pathlib.py", line 1000, in home
+      #    return cls("~").expanduser()
+      #  File "python3.10/pathlib.py", line 1440, in expanduser
+      #    raise RuntimeError("Could not determine home directory.")
+      # RuntimeError: Could not determine home directory.
+      environment.HOME = dataDir;
+
       preStart = ''
         # Not all secrets can be passed as environment variable (yet)
         # https://github.com/tulir/mautrix-telegram/issues/584