diff --git a/core/Application.php b/core/Application.php
index 2e35461015472..592e092966681 100644
--- a/core/Application.php
+++ b/core/Application.php
@@ -243,6 +243,13 @@ function (GenericEvent $event) use ($container) {
 						$subject->addHintForMissingSubject($table->getName(), 'mounts_user_root_path_index');
 					}
 				}
+
+				if ($schema->hasTable('systemtag_object_mapping')) {
+					$table = $schema->getTable('systemtag_object_mapping');
+					if (!$table->hasIndex('systag_by_tagid')) {
+						$subject->addHintForMissingSubject($table->getName(), 'systag_by_tagid');
+					}
+				}
 			}
 		);
 
diff --git a/core/Command/Db/AddMissingIndices.php b/core/Command/Db/AddMissingIndices.php
index b317f44b49930..452bcbad5dc05 100644
--- a/core/Command/Db/AddMissingIndices.php
+++ b/core/Command/Db/AddMissingIndices.php
@@ -475,6 +475,19 @@ private function addCoreIndexes(OutputInterface $output, bool $dryRun): void {
 			}
 		}
 
+		$output->writeln('<info>Check indices of the oc_systemtag_object_mapping table.</info>');
+		if ($schema->hasTable('oc_systemtag_object_mapping')) {
+			$table = $schema->getTable('oc_systemtag_object_mapping');
+			if (!$table->hasIndex('systag_by_tagid')) {
+				$output->writeln('<info>Adding systag_by_tagid index to the oc_systemtag_object_mapping table, this can take some time...</info>');
+
+				$table->addIndex(['systemtagid', 'objecttype'], 'systag_by_tagid');
+				$this->connection->migrateToSchema($schema->getWrappedSchema());
+				$updated = true;
+				$output->writeln('<info>oc_systemtag_object_mapping table updated successfully.</info>');
+			}
+		}
+
 		if (!$updated) {
 			$output->writeln('<info>Done.</info>');
 		}
diff --git a/core/Migrations/Version13000Date20170718121200.php b/core/Migrations/Version13000Date20170718121200.php
index 34a249814fbc2..05cdbcfd6b5f0 100644
--- a/core/Migrations/Version13000Date20170718121200.php
+++ b/core/Migrations/Version13000Date20170718121200.php
@@ -754,6 +754,7 @@ public function changeSchema(IOutput $output, \Closure $schemaClosure, array $op
 			]);
 			$table->setPrimaryKey(['objecttype', 'objectid', 'systemtagid'], 'som_pk');
 //			$table->addUniqueIndex(['objecttype', 'objectid', 'systemtagid'], 'mapping');
+			$table->addIndex(['systemtagid', 'objecttype'], 'systag_by_tagid');
 		}
 
 		if (!$schema->hasTable('systemtag_group')) {