diff --git a/lib/private/Files/Cache/Cache.php b/lib/private/Files/Cache/Cache.php
index ae707fb5b54..99be91f5d6b 100644
--- a/lib/private/Files/Cache/Cache.php
+++ b/lib/private/Files/Cache/Cache.php
@@ -840,7 +840,13 @@ class Cache implements ICache {
 	protected function buildSearchQuery(ISearchQuery $searchQuery): IQueryBuilder {
 		$builder = $this->getQueryBuilder();
 
-		$query = $builder->selectFileCache('file');
+		// mysql really likes to pick an index for sorting if it can't fully satisfy the where
+		// filter with an index, since search queries pretty much never are fully filtered by index
+		// mysql often picks an index for sorting instead of the *much* more useful index for filtering.
+		//
+		// To bypass this, we tell mysql explicitly not to use the mtime (the default order field) index,
+		// so it will instead pick an index that is actually useful.
+		$query = $builder->selectFileCache('file', 'ignore index for order by (fs_mtime)');
 
 		$query->whereStorageId();