diff --git a/lib/private/Share20/Share.php b/lib/private/Share20/Share.php
index 6edd0e6886a..c361f01216f 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/illegalidchangeexception.php b/lib/public/share/exceptions/illegalidchangeexception.php
new file mode 100644
index 00000000000..6cd887c386b
--- /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/ishare.php b/lib/public/share/ishare.php
index fdf40f19e56..ee71715f436 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/tests/lib/share20/defaultshareprovidertest.php b/tests/lib/share20/defaultshareprovidertest.php
index 610de3b6232..8d8ae8d4809 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());