diff --git a/nixos/modules/services/databases/mysql.nix b/nixos/modules/services/databases/mysql.nix
index c8545d327af..5f184df34c6 100644
--- a/nixos/modules/services/databases/mysql.nix
+++ b/nixos/modules/services/databases/mysql.nix
@@ -23,6 +23,7 @@ let
   ''
     [mysqld]
     port = ${toString cfg.port}
+    datadir = ${cfg.dataDir}
     ${optionalString (cfg.bind != null) "bind-address = ${cfg.bind}" }
     ${optionalString (cfg.replication.role == "master" || cfg.replication.role == "slave") "log-bin=mysql-bin"}
     ${optionalString (cfg.replication.role == "master" || cfg.replication.role == "slave") "server-id = ${toString cfg.replication.serverId}"}