diff --git a/apps/files_external/lib/Lib/Storage/AmazonS3.php b/apps/files_external/lib/Lib/Storage/AmazonS3.php
index 801de49960a66..e5e1d8485f32d 100644
--- a/apps/files_external/lib/Lib/Storage/AmazonS3.php
+++ b/apps/files_external/lib/Lib/Storage/AmazonS3.php
@@ -645,6 +645,12 @@ public function getDirectoryContent(string $directory): \Traversable {
 			// sub folders
 			if (is_array($result['CommonPrefixes'])) {
 				foreach ($result['CommonPrefixes'] as $prefix) {
+					if (preg_match('/\/{2,}$/', $prefix['Prefix'])) {
+						$this->logger->warning('Detected a repeating delimiter in prefix \'' . $prefix['Prefix']
+											   . '\'. This is unsupported and its contents have been ignored.');
+						continue;
+					}
+
 					$dir = $this->getDirectoryMetaData($prefix['Prefix']);
 					if ($dir) {
 						yield $dir;