diff --git a/lib/Controller/FolderController.php b/lib/Controller/FolderController.php
index 1344f08c0..0293a2019 100644
--- a/lib/Controller/FolderController.php
+++ b/lib/Controller/FolderController.php
@@ -90,7 +90,7 @@ private function formatFolder(array $folder): array {
 	 * Gets all Groupfolders
 	 *
 	 * @param bool $applicable Filter by applicable groups
-	 * @return DataResponse<Http::STATUS_OK, list<GroupFoldersFolder>, array{}>
+	 * @return DataResponse<Http::STATUS_OK, array<string, GroupFoldersFolder>, array{}>
 	 * @throws OCSNotFoundException Storage not found
 	 *
 	 * 200: Groupfolders returned
@@ -103,8 +103,11 @@ public function getFolders(bool $applicable = false): DataResponse {
 			throw new OCSNotFoundException();
 		}
 
-		$folders = array_values($this->manager->getAllFoldersWithSize($storageId));
-		$folders = array_map($this->formatFolder(...), $folders);
+		$folders = [];
+		foreach ($this->manager->getAllFoldersWithSize($storageId) as $id => $folder) {
+			// Make them string-indexed for OpenAPI JSON output
+			$folders[(string)$id] = $this->formatFolder($folder);
+		}
 		$isAdmin = $this->delegationService->isAdminNextcloud() || $this->delegationService->isDelegatedAdmin();
 		if ($isAdmin && !$applicable) {
 			return new DataResponse($folders);
@@ -115,7 +118,7 @@ public function getFolders(bool $applicable = false): DataResponse {
 		}
 
 		if ($applicable || !$this->delegationService->hasApiAccess()) {
-			$folders = array_values(array_filter(array_map($this->filterNonAdminFolder(...), $folders)));
+			$folders = array_filter(array_map($this->filterNonAdminFolder(...), $folders));
 		}
 
 		return new DataResponse($folders);
diff --git a/lib/Service/FoldersFilter.php b/lib/Service/FoldersFilter.php
index dcb6fb0d6..2f3af74d2 100644
--- a/lib/Service/FoldersFilter.php
+++ b/lib/Service/FoldersFilter.php
@@ -22,8 +22,8 @@ public function __construct(
 	}
 
 	/**
-	 * @param list<GroupFoldersFolder> $folders List of all folders
-	 * @return list<GroupFoldersFolder>
+	 * @param GroupFoldersFolder[] $folders List of all folders
+	 * @return GroupFoldersFolder[]
 	 */
 	public function getForApiUser(array $folders): array {
 		$user = $this->userSession->getUser();
diff --git a/openapi.json b/openapi.json
index 7233e88aa..42f11ea0c 100644
--- a/openapi.json
+++ b/openapi.json
@@ -389,8 +389,8 @@
                         "content": {
                             "application/json": {
                                 "schema": {
-                                    "type": "array",
-                                    "items": {
+                                    "type": "object",
+                                    "additionalProperties": {
                                         "$ref": "#/components/schemas/Folder"
                                     }
                                 }
diff --git a/src/types/openapi/openapi.ts b/src/types/openapi/openapi.ts
index 1fff7ad55..4420830e5 100644
--- a/src/types/openapi/openapi.ts
+++ b/src/types/openapi/openapi.ts
@@ -400,7 +400,9 @@ export interface operations {
                     [name: string]: unknown;
                 };
                 content: {
-                    "application/json": components["schemas"]["Folder"][];
+                    "application/json": {
+                        [key: string]: components["schemas"]["Folder"];
+                    };
                 };
             };
             /** @description Storage not found */