diff --git a/lib/Db/Circle.php b/lib/Db/Circle.php
index 6ea1e39eb..f4a4fa568 100644
--- a/lib/Db/Circle.php
+++ b/lib/Db/Circle.php
@@ -24,13 +24,15 @@
 namespace OCA\Deck\Db;
 
 
+use OCP\Share\IShare;
+
 class Circle extends RelationalObject {
 
 	/** @var \OCA\Circles\Model\Circle */
 	protected $object;
 
 	public function __construct(\OCA\Circles\Model\Circle $circle) {
-		$primaryKey = $circle->getUniqueId();
+		$primaryKey = IShare::TYPE_CIRCLE . ':' . $circle->getUniqueId();
 		parent::__construct($primaryKey, $circle);
 	}
 
@@ -42,4 +44,4 @@ class Circle extends RelationalObject {
 			'circleOwner' => $this->object->getOwner()
 		];
 	}
-}
\ No newline at end of file
+}
diff --git a/lib/Db/Group.php b/lib/Db/Group.php
index f668282b7..330b592d2 100644
--- a/lib/Db/Group.php
+++ b/lib/Db/Group.php
@@ -24,11 +24,12 @@
 namespace OCA\Deck\Db;
 
 use OCP\IGroup;
+use OCP\Share\IShare;
 
 class Group extends RelationalObject {
 
 	public function __construct(IGroup $group) {
-		$primaryKey = $group->getGID();
+		$primaryKey = IShare::TYPE_GROUP . ':' . $group->getGID();
 		parent::__construct($primaryKey, $group);
 	}
 
@@ -38,4 +39,4 @@ class Group extends RelationalObject {
 			'displayname' => $this->object->getDisplayName()
 		];
 	}
-}
\ No newline at end of file
+}
diff --git a/lib/Db/User.php b/lib/Db/User.php
index 89a386a8e..6f6d70ce0 100644
--- a/lib/Db/User.php
+++ b/lib/Db/User.php
@@ -24,11 +24,12 @@
 namespace OCA\Deck\Db;
 
 use OCP\IUser;
+use OCP\Share\IShare;
 
 class User extends RelationalObject {
 
 	public function __construct(IUser $user) {
-		$primaryKey = $user->getUID();
+		$primaryKey = IShare::TYPE_USER . ':' . $user->getUID();
 		parent::__construct($primaryKey, $user);
 	}
 
@@ -46,4 +47,4 @@ class User extends RelationalObject {
 	public function getDisplayName() {
 		return $this->object->getDisplayName();
 	}
-}
\ No newline at end of file
+}
diff --git a/lib/Service/AssignmentService.php b/lib/Service/AssignmentService.php
index 418bbd9fa..0ba1071a3 100644
--- a/lib/Service/AssignmentService.php
+++ b/lib/Service/AssignmentService.php
@@ -126,7 +126,7 @@ class AssignmentService {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
 		$assignments = $this->assignedUsersMapper->find($cardId);
 		foreach ($assignments as $assignment) {
-			if ($assignment->getParticipant() === $userId) {
+			if ($assignment->getParticipant() === $userId && $assignment->getType() === $type) {
 				throw new BadRequestException('The user is already assigned to the card');
 			}
 		}
diff --git a/src/components/board/SharingTabSidebar.vue b/src/components/board/SharingTabSidebar.vue
index be1789178..7fd82d148 100644
--- a/src/components/board/SharingTabSidebar.vue
+++ b/src/components/board/SharingTabSidebar.vue
@@ -23,7 +23,7 @@
 					</span>
 				</span>
 			</li>
-			<li v-for="acl in board.acl" :key="acl.participant.uid">
+			<li v-for="acl in board.acl" :key="acl.participant.primaryKey">
 				<Avatar v-if="acl.type===0" :user="acl.participant.uid" />
 				<div v-if="acl.type===1" class="avatardiv icon icon-group" />
 				<div v-if="acl.type===7" class="avatardiv icon icon-circles" />
@@ -33,10 +33,10 @@
 					<span v-if="acl.type===7">{{ t('deck', '(Circle)') }}</span>
 				</span>
 
-				<ActionCheckbox v-if="!isCurrentUser(acl.participant.uid) && (canManage || (canEdit && canShare))" :checked="acl.permissionEdit" @change="clickEditAcl(acl)">
+				<ActionCheckbox v-if="!(isCurrentUser(acl.participant.uid) && acl.type === 0) && (canManage || (canEdit && canShare))" :checked="acl.permissionEdit" @change="clickEditAcl(acl)">
 					{{ t('deck', 'Can edit') }}
 				</ActionCheckbox>
-				<Actions v-if="!isCurrentUser(acl.participant.uid)" :force-menu="true">
+				<Actions v-if="!(isCurrentUser(acl.participant.uid) && acl.type === 0)" :force-menu="true">
 					<ActionCheckbox v-if="canManage || canShare" :checked="acl.permissionShare" @change="clickShareAcl(acl)">
 						{{ t('deck', 'Can share') }}
 					</ActionCheckbox>
diff --git a/src/components/card/CardSidebar.vue b/src/components/card/CardSidebar.vue
index e0b7551f0..c6b1fe0a0 100644
--- a/src/components/card/CardSidebar.vue
+++ b/src/components/card/CardSidebar.vue
@@ -61,10 +61,9 @@
 
 			<div class="section-wrapper">
 				<div v-tooltip="t('deck', 'Assign to users')" class="section-label icon-group">
-					<span class="hidden-visually">{{ t('deck', 'Assign to users') }}</span>
+					<span class="hidden-visually">{{ t('deck', 'Assign to users/groups/circles') }}</span>
 				</div>
 				<div class="section-details">
-					<!-- FIXME: model not wokring due to id -->
 					<Multiselect v-if="canEdit"
 						v-model="assignedUsers"
 						:multiple="true"
@@ -78,7 +77,7 @@
 						@remove="removeUserFromCard">
 						<template #tag="scope">
 							<div class="avatarlist--inline">
-								<Avatar :user="scope.option.primaryKey"
+								<Avatar :user="scope.option.uid"
 									:display-name="scope.option.displayname"
 									:size="24"
 									:disable-menu="true" />
@@ -87,8 +86,8 @@
 					</Multiselect>
 					<div v-else class="avatar-list--readonly">
 						<Avatar v-for="option in currentCard.assignedUsers"
-							:key="option.id"
-							:user="option.participant.primaryKey"
+							:key="option.primaryKey"
+							:user="option.participant.uid"
 							:display-name="option.participant.displayname"
 							:size="32" />
 					</div>
diff --git a/src/components/card/CommentForm.vue b/src/components/card/CommentForm.vue
index 430e54925..4601e7dff 100644
--- a/src/components/card/CommentForm.vue
+++ b/src/components/card/CommentForm.vue
@@ -26,7 +26,7 @@
 			<At ref="at"
 				v-model="commentText"
 				:members="members"
-				name-key="primaryKey"
+				name-key="uid"
 				:tab-select="true">
 				<template v-slot:item="s">
 					<Avatar class="atwho-li--avatar" :user="s.item.uid" :size="24" />
@@ -34,9 +34,9 @@
 				</template>
 				<template v-slot:embeddedItem="scope">
 					<span>
-						<UserBubble v-if="scope.current.primaryKey"
-							:data-mention-id="scope.current.primaryKey"
-							:user="scope.current.primaryKey"
+						<UserBubble v-if="scope.current.uid"
+							:data-mention-id="scope.current.uid"
+							:user="scope.current.uid"
 							:display-name="scope.current.displayname" />
 					</span>
 				</template>
diff --git a/src/components/cards/AvatarList.vue b/src/components/cards/AvatarList.vue
index 80e5c40fb..95b9f2a6e 100644
--- a/src/components/cards/AvatarList.vue
+++ b/src/components/cards/AvatarList.vue
@@ -34,15 +34,15 @@
 					:size="32" />
 				<Avatar v-if="user.type === 1"
 					:user="user.participant.primaryKey"
-					:display-name="user.participant.primaryKey"
-					:tooltip-message="user.participant.primaryKey + ' ' + t('deck', '(group)')"
+					:display-name="user.participant.displayname"
+					:tooltip-message="user.participant.displayname + ' ' + t('deck', '(group)')"
 					:is-no-user="true"
 					:disable-="true"
 					:size="32" />
 				<Avatar v-if="user.type === 7"
 					:user="user.participant.primaryKey"
-					:display-name="user.participant.primaryKey"
-					:tooltip-message="user.participant.primaryKey + ' ' + t('deck', '(circle)')"
+					:display-name="user.participant.displayname"
+					:tooltip-message="user.participant.displayname + ' ' + t('deck', '(circle)')"
 					:is-no-user="true"
 					:disable-="true"
 					:size="32" />
@@ -91,7 +91,7 @@ export default {
 				if (assignable.type === 1) {
 					return 'icon-group'
 				}
-				const user = assignable.participant.primaryKey
+				const user = assignable.participant.uid
 				const size = 32
 				const avatarUrl = OC.generateUrl('/avatar/{user}/{size}',
 					{
diff --git a/tests/unit/Db/GroupTest.php b/tests/unit/Db/GroupTest.php
index 8f0678c62..163974871 100644
--- a/tests/unit/Db/GroupTest.php
+++ b/tests/unit/Db/GroupTest.php
@@ -57,7 +57,7 @@ class GroupTest extends \Test\TestCase {
 		$expected = [
 			'uid' => 'mygroup',
 			'displayname' => 'My Group',
-			'primaryKey' => 'mygroup'
+			'primaryKey' => '1:mygroup'
 		];
 
 		$actual = $groupRelationalObject->jsonSerialize();
diff --git a/tests/unit/Db/UserTest.php b/tests/unit/Db/UserTest.php
index 43b15dda1..221a7f06d 100644
--- a/tests/unit/Db/UserTest.php
+++ b/tests/unit/Db/UserTest.php
@@ -57,8 +57,8 @@ class UserTest extends \Test\TestCase {
 		$expected = [
 			'uid' => 'myuser',
 			'displayname' => 'myuser displayname',
-			'primaryKey' => 'myuser'
+			'primaryKey' => '0:myuser'
 		];
 		$this->assertEquals($expected, $userRelationalObject->jsonSerialize());
 	}
-}
\ No newline at end of file
+}