diff --git a/app/server/lib/FlexServer.ts b/app/server/lib/FlexServer.ts
index 72a55f13..1aa73ea2 100644
--- a/app/server/lib/FlexServer.ts
+++ b/app/server/lib/FlexServer.ts
@@ -1132,9 +1132,6 @@ export class FlexServer implements GristServer {
     await this.loadConfig();
     this.addComm();
 
-    // Temporary duplication of external storage configuration.
-    // This may break https://github.com/gristlabs/grist-core/pull/546,
-    // but will revive other uses of external storage. TODO: reconcile.
     await this.create.configure?.();
 
     if (!isSingleUserMode()) {
@@ -1147,7 +1144,7 @@ export class FlexServer implements GristServer {
         this._disableExternalStorage = true;
         externalStorage.flag('active').set(false);
       }
-      await this.create.configure?.();
+      await this.create.checkBackend?.();
       const workers = this._docWorkerMap;
       const docWorkerId = await this._addSelfAsWorker(workers);
 
diff --git a/app/server/lib/ICreate.ts b/app/server/lib/ICreate.ts
index f876fa9c..73b76e5c 100644
--- a/app/server/lib/ICreate.ts
+++ b/app/server/lib/ICreate.ts
@@ -32,6 +32,8 @@ export interface ICreate {
   sessionSecret(): string;
   // Check configuration of the app early enough to show on startup.
   configure?(): Promise<void>;
+  // Optionally perform sanity checks on the configured storage, throwing a fatal error if it is not functional
+  checkBackend?(): Promise<void>;
   // Return a string containing 1 or more HTML tags to insert into the head element of every
   // static page.
   getExtraHeadHtml?(): string;
@@ -119,6 +121,13 @@ export function makeSimpleCreator(opts: {
       return secret;
     },
     async configure() {
+      for (const s of storage || []) {
+        if (s.check()) {
+          break;
+        }
+      }
+    },
+    async checkBackend() {
       for (const s of storage || []) {
         if (s.check()) {
           await s.checkBackend?.();