diff --git a/app/server/lib/DocSnapshots.ts b/app/server/lib/DocSnapshots.ts
index 01b1f5a1..a353502f 100644
--- a/app/server/lib/DocSnapshots.ts
+++ b/app/server/lib/DocSnapshots.ts
@@ -148,7 +148,29 @@ export class DocSnapshotInventory implements IInventory {
    * The snapshot supplied will be modified in place to a normalized form.
    */
   public async add(key: string, snapshot: ObjSnapshotWithMetadata, prevSnapshotId: string|null) {
+    await this.uploadAndAdd(key, async () => {
+      return { snapshot, prevSnapshotId };
+    });
+  }
+
+  /**
+   * Like add(), but takes an "upload" callback that allows
+   * preparing snapshot and prevSnapshotId atomically with the
+   * rest of the add operation, and thus serialized with any
+   * other operations such as versions(). This is important since an
+   * upload changes the list of versions as far as the external store
+   * is concerned, which could trigger a "surprise" and a full reload
+   * of the version list.
+   */
+  public async uploadAndAdd(key: string,
+                            upload: () => Promise<{snapshot?: ObjSnapshotWithMetadata,
+                                                   prevSnapshotId: string|null}>) {
     await this._mutex.runExclusive(key, async() => {
+      const {snapshot, prevSnapshotId} = await upload();
+      if (!snapshot) {
+        // the upload generated no snapshot, so there is nothing to do.
+        return;
+      }
       const snapshots = await this._getSnapshots(key, prevSnapshotId);
       // Could be already added if reconstruction happened.
       if (snapshots[0] && snapshots[0].snapshotId === snapshot.snapshotId) { return; }
diff --git a/app/server/lib/HostedStorageManager.ts b/app/server/lib/HostedStorageManager.ts
index ac33b4e1..30f64298 100644
--- a/app/server/lib/HostedStorageManager.ts
+++ b/app/server/lib/HostedStorageManager.ts
@@ -739,23 +739,29 @@ export class HostedStorageManager implements IDocStorageManager {
         ...label && {label},
         t,
       };
-      const prevSnapshotId = this._latestVersions.get(docId) || null;
-      const newSnapshotId = await this._ext.upload(docId, tmpPath, metadata);
-      if (newSnapshotId === Unchanged) {
-        // Nothing uploaded because nothing changed
-        return;
+      let changeMade: boolean = false;
+      await this._inventory.uploadAndAdd(docId, async () => {
+        const prevSnapshotId = this._latestVersions.get(docId) || null;
+        const newSnapshotId = await this._ext.upload(docId, tmpPath as string, metadata);
+        if (newSnapshotId === Unchanged) {
+          // Nothing uploaded because nothing changed
+          return { prevSnapshotId };
+        }
+        if (!newSnapshotId) {
+          // This is unexpected.
+          throw new Error('No snapshotId allocated after upload');
+        }
+        const snapshot = {
+          lastModified: t,
+          snapshotId: newSnapshotId,
+          metadata
+        };
+        changeMade = true;
+        return { snapshot, prevSnapshotId };
+      });
+      if (changeMade) {
+        await this._onInventoryChange(docId);
       }
-      if (!newSnapshotId) {
-        // This is unexpected.
-        throw new Error('No snapshotId allocated after upload');
-      }
-      const snapshot = {
-        lastModified: t,
-        snapshotId: newSnapshotId,
-        metadata
-      };
-      await this._inventory.add(docId, snapshot, prevSnapshotId);
-      await this._onInventoryChange(docId);
     } finally {
       // Clean up backup.
       // NOTE: fse.remove succeeds also when the file does not exist.