diff --git a/keyserver/src/database/db-config.js b/keyserver/src/database/db-config.js
index 8b7e037b7..f9e87d7a6 100644
--- a/keyserver/src/database/db-config.js
+++ b/keyserver/src/database/db-config.js
@@ -1,56 +1,63 @@
 // @flow
 
 import invariant from 'invariant';
 
 import { importJSON } from '../utils/import-json';
 
 type DBType = 'mysql5.7' | 'mariadb10.8';
 export type DBConfig = {
   +host: string,
   +user: string,
   +password: string,
   +database: string,
   +dbType: DBType,
 };
 
+function assertValidDBType(dbType: ?string): DBType {
+  if (!dbType) {
+    return 'mysql5.7';
+  }
+  invariant(
+    dbType === 'mysql5.7' || dbType === 'mariadb10.8',
+    `${dbType} is not a valid dbType`,
+  );
+  return dbType;
+}
+
 let dbConfig;
 async function getDBConfig(): Promise<DBConfig> {
   if (dbConfig !== undefined) {
     return dbConfig;
   }
   if (
     process.env.COMM_DATABASE_DATABASE &&
     process.env.COMM_DATABASE_USER &&
     process.env.COMM_DATABASE_PASSWORD
   ) {
     dbConfig = {
       host: process.env.COMM_DATABASE_HOST || 'localhost',
       user: process.env.COMM_DATABASE_USER,
       password: process.env.COMM_DATABASE_PASSWORD,
       database: process.env.COMM_DATABASE_DATABASE,
-      dbType:
-        process.env.COMM_DATABASE_TYPE === 'mariadb10.8'
-          ? 'mariadb10.8'
-          : 'mysql5.7',
+      dbType: assertValidDBType(process.env.COMM_DATABASE_TYPE),
     };
   } else {
     const importedDBConfig = await importJSON({
       folder: 'secrets',
       name: 'db_config',
     });
     invariant(importedDBConfig, 'DB config missing');
     dbConfig = {
       ...importedDBConfig,
-      dbType:
-        importedDBConfig.dbType === 'mariadb10.8' ? 'mariadb10.8' : 'mysql5.7',
+      dbType: assertValidDBType(importedDBConfig.dbType),
     };
   }
   return dbConfig;
 }
 
 async function getDBType(): Promise<DBType> {
   const config = await getDBConfig();
   return config.dbType;
 }
 
 export { getDBConfig, getDBType };