diff --git a/core/Application.php b/core/Application.php
index 34932cab18399..8775b9cf88be4 100644
--- a/core/Application.php
+++ b/core/Application.php
@@ -218,6 +218,13 @@ function (GenericEvent $event) use ($container) {
 						$subject->addHintForMissingSubject($table->getName(), 'direct_edit_timestamp');
 					}
 				}
+
+				if ($schema->hasTable('mounts')) {
+					$table = $schema->getTable('mounts');
+					if (!$table->hasIndex('mounts_class_index')) {
+						$subject->addHintForMissingSubject($table->getName(), 'mounts_class_index');
+					}
+				}
 			}
 		);
 
diff --git a/core/Command/Db/AddMissingIndices.php b/core/Command/Db/AddMissingIndices.php
index a4379ffacc3be..c31acdb122537 100644
--- a/core/Command/Db/AddMissingIndices.php
+++ b/core/Command/Db/AddMissingIndices.php
@@ -435,6 +435,22 @@ private function addCoreIndexes(OutputInterface $output, bool $dryRun): void {
 			}
 		}
 
+		$output->writeln('<info>Check indices of the oc_mounts table.</info>');
+		if ($schema->hasTable('mounts')) {
+			$table = $schema->getTable('mounts');
+			if (!$table->hasIndex('mounts_class_index')) {
+				$output->writeln('<info>Adding mounts_class_index index to the oc_mounts table, this can take some time...</info>');
+
+				$table->addIndex(['mount_provider_class'], 'mounts_class_index');
+				$sqlQueries = $this->connection->migrateToSchema($schema->getWrappedSchema(), $dryRun);
+				if ($dryRun && $sqlQueries !== null) {
+					$output->writeln($sqlQueries);
+				}
+				$updated = true;
+				$output->writeln('<info>oc_mounts table updated successfully.</info>');
+			}
+		}
+
 		if (!$updated) {
 			$output->writeln('<info>Done.</info>');
 		}
diff --git a/core/Migrations/Version24000Date20220202150027.php b/core/Migrations/Version24000Date20220202150027.php
index 76a3ae8c73c1e..6a3f5ad2faf9b 100644
--- a/core/Migrations/Version24000Date20220202150027.php
+++ b/core/Migrations/Version24000Date20220202150027.php
@@ -30,6 +30,7 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 				'notnull' => false,
 				'length' => 128,
 			]);
+			$table->addIndex(['mount_provider_class'], 'mounts_class_index');
 			return $schema;
 		}
 		return null;