diff --git a/apps/files_external/lib/config/configadapter.php b/apps/files_external/lib/config/configadapter.php
index a255a7b3d2..cb8c2f24ca 100644
--- a/apps/files_external/lib/config/configadapter.php
+++ b/apps/files_external/lib/config/configadapter.php
@@ -114,7 +114,7 @@ class ConfigAdapter implements IMountProvider {
 		$this->userStoragesService->setUser($user);
 		$this->userGlobalStoragesService->setUser($user);
 
-		foreach ($this->userGlobalStoragesService->getAllStorages() as $storage) {
+		foreach ($this->userGlobalStoragesService->getUniqueStorages() as $storage) {
 			try {
 				$this->prepareStorageConfig($storage, $user);
 				$impl = $this->constructStorage($storage);
diff --git a/apps/files_external/service/userglobalstoragesservice.php b/apps/files_external/service/userglobalstoragesservice.php
index c59652d057..b60473f131 100644
--- a/apps/files_external/service/userglobalstoragesservice.php
+++ b/apps/files_external/service/userglobalstoragesservice.php
@@ -26,6 +26,7 @@ use \OCA\Files_External\Service\BackendService;
 use \OCP\IUserSession;
 use \OCP\IGroupManager;
 use \OCA\Files_External\Service\UserTrait;
+use \OCA\Files_External\Lib\StorageConfig;
 
 /**
  * Service class to read global storages applicable to the user
@@ -109,4 +110,60 @@ class UserGlobalStoragesService extends GlobalStoragesService {
 		throw new \DomainException('UserGlobalStoragesService writing disallowed');
 	}
 
+	/**
+	 * Get unique storages, in case two are defined with the same mountpoint
+	 * Higher priority storages take precedence
+	 *
+	 * @return StorageConfig[]
+	 */
+	public function getUniqueStorages() {
+		$storages = $this->getAllStorages();
+
+		$storagesByMountpoint = [];
+		foreach ($storages as $storage) {
+			$storagesByMountpoint[$storage->getMountPoint()][] = $storage;
+		}
+
+		$result = [];
+		foreach ($storagesByMountpoint as $storageList) {
+			$storage = array_reduce($storageList, function($carry, $item) {
+				if (isset($carry)) {
+					$carryPriorityType = $this->getPriorityType($carry);
+					$itemPriorityType = $this->getPriorityType($item);
+					if ($carryPriorityType > $itemPriorityType) {
+						return $carry;
+					} elseif ($carryPriorityType === $itemPriorityType) {
+						if ($carry->getPriority() > $item->getPriority()) {
+							return $carry;
+						}
+					}
+				}
+				return $item;
+			});
+			$result[$storage->getID()] = $storage;
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Get a priority 'type', where a bigger number means higher priority
+	 * user applicable > group applicable > 'all'
+	 *
+	 * @param StorageConfig $storage
+	 * @return int
+	 */
+	protected function getPriorityType(StorageConfig $storage) {
+		$applicableUsers = $storage->getApplicableUsers();
+		$applicableGroups = $storage->getApplicableGroups();
+
+		if ($applicableUsers && $applicableUsers[0] !== 'all') {
+			return 2;
+		}
+		if ($applicableGroups) {
+			return 1;
+		}
+		return 0;
+	}
+
 }
diff --git a/apps/files_external/tests/service/userglobalstoragesservicetest.php b/apps/files_external/tests/service/userglobalstoragesservicetest.php
index b9e2c08c93..867872f368 100644
--- a/apps/files_external/tests/service/userglobalstoragesservicetest.php
+++ b/apps/files_external/tests/service/userglobalstoragesservicetest.php
@@ -35,6 +35,7 @@ class UserGlobalStoragesServiceTest extends GlobalStoragesServiceTest {
 
 	const USER_ID = 'test_user';
 	const GROUP_ID = 'test_group';
+	const GROUP_ID2 = 'test_group2';
 
 	public function setUp() {
 		parent::setUp();
@@ -51,8 +52,12 @@ class UserGlobalStoragesServiceTest extends GlobalStoragesServiceTest {
 		$this->groupManager = $this->getMock('\OCP\IGroupManager');
 		$this->groupManager->method('isInGroup')
 			->will($this->returnCallback(function($userId, $groupId) {
-				if ($userId === self::USER_ID && $groupId === self::GROUP_ID) {
-					return true;
+				if ($userId === self::USER_ID) {
+					switch ($groupId) {
+					case self::GROUP_ID:
+					case self::GROUP_ID2:
+						return true;
+					}
 				}
 				return false;
 			}));
@@ -167,6 +172,77 @@ class UserGlobalStoragesServiceTest extends GlobalStoragesServiceTest {
 		$this->service->removeStorage(1);
 	}
 
+	public function getUniqueStoragesProvider() {
+		return [
+			// 'all' vs group
+			[100, [], [], 100, [], [self::GROUP_ID], 2],
+			[100, [], [self::GROUP_ID], 100, [], [], 1],
+
+			// 'all' vs user
+			[100, [], [], 100, [self::USER_ID], [], 2],
+			[100, [self::USER_ID], [], 100, [], [], 1],
+
+			// group vs user
+			[100, [], [self::GROUP_ID], 100, [self::USER_ID], [], 2],
+			[100, [self::USER_ID], [], 100, [], [self::GROUP_ID], 1],
+
+			// group+user vs group
+			[100, [], [self::GROUP_ID2], 100, [self::USER_ID], [self::GROUP_ID], 2],
+			[100, [self::USER_ID], [self::GROUP_ID], 100, [], [self::GROUP_ID2], 1],
+
+			// user vs 'all' (higher priority)
+			[200, [], [], 100, [self::USER_ID], [], 2],
+			[100, [self::USER_ID], [], 200, [], [], 1],
+
+			// group vs group (higher priority)
+			[100, [], [self::GROUP_ID2], 200, [], [self::GROUP_ID], 2],
+			[200, [], [self::GROUP_ID], 100, [], [self::GROUP_ID2], 1],
+		];
+	}
+
+	/**
+	 * @dataProvider getUniqueStoragesProvider
+	 */
+	public function testGetUniqueStorages(
+		$priority1, $applicableUsers1, $applicableGroups1,
+		$priority2, $applicableUsers2, $applicableGroups2,
+		$expectedPrecedence
+	) {
+		$backend = $this->backendService->getBackend('identifier:\OCA\Files_External\Lib\Backend\SMB');
+		$authMechanism = $this->backendService->getAuthMechanism('identifier:\Auth\Mechanism');
+
+		$storage1 = new StorageConfig();
+		$storage1->setMountPoint('mountpoint');
+		$storage1->setBackend($backend);
+		$storage1->setAuthMechanism($authMechanism);
+		$storage1->setBackendOptions(['password' => 'testPassword']);
+		$storage1->setPriority($priority1);
+		$storage1->setApplicableUsers($applicableUsers1);
+		$storage1->setApplicableGroups($applicableGroups1);
+
+		$storage1 = $this->globalStoragesService->addStorage($storage1);
+
+		$storage2 = new StorageConfig();
+		$storage2->setMountPoint('mountpoint');
+		$storage2->setBackend($backend);
+		$storage2->setAuthMechanism($authMechanism);
+		$storage2->setBackendOptions(['password' => 'testPassword']);
+		$storage2->setPriority($priority2);
+		$storage2->setApplicableUsers($applicableUsers2);
+		$storage2->setApplicableGroups($applicableGroups2);
+
+		$storage2 = $this->globalStoragesService->addStorage($storage2);
+
+		$storages = $this->service->getUniqueStorages();
+		$this->assertCount(1, $storages);
+
+		if ($expectedPrecedence === 1) {
+			$this->assertArrayHasKey($storage1->getID(), $storages);
+		} elseif ($expectedPrecedence === 2) {
+			$this->assertArrayHasKey($storage2->getID(), $storages);
+		}
+	}
+
 	public function testHooksAddStorage($a = null, $b = null, $c = null) {
 		// we don't test this here
 		$this->assertTrue(true);