diff --git a/apps/files_external/service/dbconfigservice.php b/apps/files_external/service/dbconfigservice.php
index a37c541f04..9f7061eb93 100644
--- a/apps/files_external/service/dbconfigservice.php
+++ b/apps/files_external/service/dbconfigservice.php
@@ -322,10 +322,19 @@ class DBConfigService {
 	private function getMountsFromQuery(IQueryBuilder $query) {
 		$result = $query->execute();
 		$mounts = $result->fetchAll();
+		$uniqueMounts = [];
+		foreach ($mounts as $mount) {
+			$id = $mount['mount_id'];
+			if (!isset($uniqueMounts[$id])) {
+				$uniqueMounts[$id] = $mount;
+			}
+		}
+		$uniqueMounts = array_values($uniqueMounts);
 
 		$mountIds = array_map(function ($mount) {
 			return $mount['mount_id'];
-		}, $mounts);
+		}, $uniqueMounts);
+		$mountIds = array_values(array_unique($mountIds));
 
 		$applicable = $this->getApplicableForMounts($mountIds);
 		$config = $this->getConfigForMounts($mountIds);
@@ -338,7 +347,7 @@ class DBConfigService {
 			$mount['config'] = $config;
 			$mount['options'] = $options;
 			return $mount;
-		}, $mounts, $applicable, $config, $options);
+		}, $uniqueMounts, $applicable, $config, $options);
 	}
 
 	/**
diff --git a/apps/files_external/tests/service/dbconfigservicetest.php b/apps/files_external/tests/service/dbconfigservicetest.php
index c6d1add36b..b088a7078d 100644
--- a/apps/files_external/tests/service/dbconfigservicetest.php
+++ b/apps/files_external/tests/service/dbconfigservicetest.php
@@ -271,4 +271,15 @@ class DBConfigServiceTest extends TestCase {
 		$mount = $this->dbConfig->getMountById($id2);
 		$this->assertEquals('bar', $mount['auth_backend']);
 	}
+
+	public function testGetMountsForDuplicateByGroup() {
+		$id1 = $this->addMount('/test', 'foo', 'bar', 100, DBConfigService::MOUNT_TYPE_ADMIN);
+
+		$this->dbConfig->addApplicable($id1, DBConfigService::APPLICABLE_TYPE_GROUP, 'group1');
+		$this->dbConfig->addApplicable($id1, DBConfigService::APPLICABLE_TYPE_GROUP, 'group2');
+
+		$mounts = $this->dbConfig->getAdminMountsForMultiple(DBConfigService::APPLICABLE_TYPE_GROUP, ['group1', 'group2']);
+		$this->assertCount(1, $mounts);
+		$this->assertEquals($id1, $mounts[0]['mount_id']);
+	}
 }