diff --git a/lib/private/Share20/Share.php b/lib/private/Share20/Share.php
index 6edd0e6886af6ee42d7accefa581ebbab48837ff..c361f01216f995be7d4b52e8cd3840606657e8fb 100644
--- a/lib/private/Share20/Share.php
+++ b/lib/private/Share20/Share.php
@@ -26,6 +26,7 @@ use OCP\Files\Node;
 use OCP\Files\NotFoundException;
 use OCP\IUser;
 use OCP\IGroup;
+use OCP\Share\Exceptions\IllegalIDChangeException;
 
 class Share implements \OCP\Share\IShare {
 
@@ -75,7 +76,19 @@ class Share implements \OCP\Share\IShare {
 	 * @inheritdoc
 	 */
 	public function setId($id) {
-		$this->id = $id;
+		if (is_int($id)) {
+			$id = (string)$id;
+		}
+
+		if(!is_string($id)) {
+			throw new \InvalidArgumentException('String expected.');
+		}
+
+		if ($this->id !== null) {
+			throw new IllegalIDChangeException('Not allowed to assign a new internal id to a share');
+		}
+
+		$this->id = trim($id);
 		return $this;
 	}
 
@@ -100,7 +113,15 @@ class Share implements \OCP\Share\IShare {
 	 * @inheritdoc
 	 */
 	public function setProviderId($id) {
-		$this->providerId = $id;
+		if(!is_string($id)) {
+			throw new \InvalidArgumentException('String expected.');
+		}
+
+		if ($this->providerId !== null) {
+			throw new IllegalIDChangeException('Not allowed to assign a new provider id to a share');
+		}
+
+		$this->providerId = trim($id);
 		return $this;
 	}
 
diff --git a/lib/public/share/exceptions/genericshareexception.php b/lib/public/Share/Exceptions/GenericShareException.php
similarity index 100%
rename from lib/public/share/exceptions/genericshareexception.php
rename to lib/public/Share/Exceptions/GenericShareException.php
diff --git a/lib/public/Share/Exceptions/IllegalIDChangeException.php b/lib/public/Share/Exceptions/IllegalIDChangeException.php
new file mode 100644
index 0000000000000000000000000000000000000000..6cd887c386bbd61bf23f8f7b69034e793ae7813f
--- /dev/null
+++ b/lib/public/Share/Exceptions/IllegalIDChangeException.php
@@ -0,0 +1,27 @@
+<?php
+/**
+ * @author Roeland Jago Douma <rullzer@owncloud.com>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OCP\Share\Exceptions;
+
+/**
+ * Exception for illegal attempts to modify an id of a share
+ * @since 9.1.0
+ */
+class IllegalIDChangeException extends GenericShareException {}
diff --git a/lib/public/share/exceptions/sharenotfound.php b/lib/public/Share/Exceptions/ShareNotFound.php
similarity index 100%
rename from lib/public/share/exceptions/sharenotfound.php
rename to lib/public/Share/Exceptions/ShareNotFound.php
diff --git a/lib/public/share/imanager.php b/lib/public/Share/IManager.php
similarity index 100%
rename from lib/public/share/imanager.php
rename to lib/public/Share/IManager.php
diff --git a/lib/public/share/iproviderfactory.php b/lib/public/Share/IProviderFactory.php
similarity index 100%
rename from lib/public/share/iproviderfactory.php
rename to lib/public/Share/IProviderFactory.php
diff --git a/lib/public/share/ishare.php b/lib/public/Share/IShare.php
similarity index 88%
rename from lib/public/share/ishare.php
rename to lib/public/Share/IShare.php
index fdf40f19e5659e5f6ff9379a4cef19c9ad7f1ac5..ee71715f436bf5f9683d88958355bf89283bfb3b 100644
--- a/lib/public/share/ishare.php
+++ b/lib/public/Share/IShare.php
@@ -25,6 +25,7 @@ use OCP\Files\File;
 use OCP\Files\Folder;
 use OCP\Files\Node;
 use OCP\Files\NotFoundException;
+use OCP\Share\Exceptions\IllegalIDChangeException;
 
 /**
  * Interface IShare
@@ -34,6 +35,19 @@ use OCP\Files\NotFoundException;
  */
 interface IShare {
 
+	/**
+	 * Set the internal id of the share
+	 * It is only allowed to set the internal id of a share once.
+	 * Attempts to override the internal id will result in an IllegalIDChangeException
+	 *
+	 * @param string $id
+	 * @return \OCP\Share\IShare
+	 * @throws IllegalIDChangeException
+	 * @throws \InvalidArgumentException
+	 * @since 9.1.0
+	 */
+	public function setId($id);
+
 	/**
 	 * Get the internal id of the share.
 	 *
@@ -52,6 +66,19 @@ interface IShare {
 	 */
 	public function getFullId();
 
+	/**
+	 * Set the provider id of the share
+	 * It is only allowed to set the provider id of a share once.
+	 * Attempts to override the provider id will result in an IllegalIDChangeException
+	 *
+	 * @param string $id
+	 * @return \OCP\Share\IShare
+	 * @throws IllegalIDChangeException
+	 * @throws \InvalidArgumentException
+	 * @since 9.1.0
+	 */
+	public function setProviderId($id);
+
 	/**
 	 * Set the node of the file/folder that is shared
 	 *
diff --git a/lib/public/share/ishareprovider.php b/lib/public/Share/IShareProvider.php
similarity index 100%
rename from lib/public/share/ishareprovider.php
rename to lib/public/Share/IShareProvider.php
diff --git a/tests/lib/share20/defaultshareprovidertest.php b/tests/lib/share20/defaultshareprovidertest.php
index 610de3b6232436381265f17455beb349b3cb87fa..8d8ae8d4809f86b35622084fed46e3a045b78cd3 100644
--- a/tests/lib/share20/defaultshareprovidertest.php
+++ b/tests/lib/share20/defaultshareprovidertest.php
@@ -969,7 +969,7 @@ class DefaultShareProviderTest extends \Test\TestCase {
 		$this->assertCount(1, $share);
 
 		$share = $share[0];
-		$this->assertSame($id, $share->getId());
+		$this->assertSame((string)$id, $share->getId());
 		$this->assertSame('sharedWith', $share->getSharedWith());
 		$this->assertSame('shareOwner', $share->getShareOwner());
 		$this->assertSame('sharedBy', $share->getSharedBy());
diff --git a/tests/lib/share20/sharetest.php b/tests/lib/share20/sharetest.php
new file mode 100644
index 0000000000000000000000000000000000000000..fdfc69f6577bd147331f7f3bf6b4b10f45b38a96
--- /dev/null
+++ b/tests/lib/share20/sharetest.php
@@ -0,0 +1,93 @@
+<?php
+/**
+ * @author Roeland Jago Douma <rullzer@owncloud.com>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace Test\Share20;
+
+use OCP\Files\IRootFolder;
+
+/**
+ * Class ShareTest
+ *
+ * @package Test\Share20
+ */
+class ShareTest extends \Test\TestCase {
+
+	/** @var IRootFolder|\PHPUnit_Framework_MockObject_MockObject */
+	protected $rootFolder;
+	/** @var \OCP\Share\IShare */
+	protected $share;
+
+	public function setUp() {
+		$this->rootFolder = $this->getMock('\OCP\Files\IRootFolder');
+		$this->share = new \OC\Share20\Share($this->rootFolder);
+	}
+
+	/**
+	 * @expectedException \InvalidArgumentException
+	 * @expectedExceptionMessage String expected.
+	 */
+	public function testSetIdInvalid() {
+		$this->share->setId(1.2);
+	}
+
+	public function testSetIdInt() {
+		$this->share->setId(42);
+		$this->assertEquals('42', $this->share->getId());
+	}
+
+
+	public function testSetIdString() {
+		$this->share->setId('foo');
+		$this->assertEquals('foo', $this->share->getId());
+	}
+
+	/**
+	 * @expectedException \OCP\Share\Exceptions\IllegalIDChangeException
+	 * @expectedExceptionMessage Not allowed to assign a new internal id to a share
+	 */
+	public function testSetIdOnce() {
+		$this->share->setId('foo');
+		$this->share->setId('bar');
+	}
+
+	/**
+	 * @expectedException \InvalidArgumentException
+	 * @expectedExceptionMessage String expected.
+	 */
+	public function testSetProviderIdInt() {
+		$this->share->setProviderId(42);
+	}
+
+
+	public function testSetProviderIdString() {
+		$this->share->setProviderId('foo');
+		$this->share->setId('bar');
+		$this->assertEquals('foo:bar', $this->share->getFullId());
+	}
+
+	/**
+	 * @expectedException \OCP\Share\Exceptions\IllegalIDChangeException
+	 * @expectedExceptionMessage Not allowed to assign a new provider id to a share
+	 */
+	public function testSetProviderIdOnce() {
+		$this->share->setProviderId('foo');
+		$this->share->setProviderId('bar');
+	}
+}