diff --git a/phpBB/adm/style/acp_users.html b/phpBB/adm/style/acp_users.html
index da7d2a495b..e266654649 100644
--- a/phpBB/adm/style/acp_users.html
+++ b/phpBB/adm/style/acp_users.html
@@ -135,8 +135,8 @@
 		<!-- ELSE -->
 			<!-- IF group.S_ROW_COUNT is even --><tr class="row1"><!-- ELSE --><tr class="row2"><!-- ENDIF -->
 				<td><a href="{group.U_EDIT_GROUP}">{group.GROUP_NAME}</a></td>
-				<td><!-- IF group.S_NO_DEFAULT --><a href="{group.U_DEFAULT}">{L_GROUP_DEFAULT}</a><!-- ELSE --><strong>{L_GROUP_DEFAULT}</strong><!-- ENDIF --></td>
-				<td><!-- IF not group.S_SPECIAL_GROUP --><a href="{group.U_DEMOTE_PROMOTE}">{group.L_DEMOTE_PROMOTE}</a><!-- ELSE -->&nbsp;<!-- ENDIF --></td>
+				<td><!-- IF group.S_IS_MEMBER --><!-- IF group.S_NO_DEFAULT --><a href="{group.U_DEFAULT}">{L_GROUP_DEFAULT}</a><!-- ELSE --><strong>{L_GROUP_DEFAULT}</strong><!-- ENDIF --><!-- ELSEIF not group.S_IS_MEMBER and group.U_APPROVE --><a href="{group.U_APPROVE}">{L_GROUP_APPROVE}</a><!-- ELSE -->&nbsp;<!-- ENDIF --></td>
+				<td><!-- IF group.S_IS_MEMBER and not group.S_SPECIAL_GROUP --><a href="{group.U_DEMOTE_PROMOTE}">{group.L_DEMOTE_PROMOTE}</a><!-- ELSE -->&nbsp;<!-- ENDIF --></td>
 				<td><a href="{group.U_DELETE}">{L_GROUP_DELETE}</a></td>
 			</tr>
 		<!-- ENDIF -->
diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index 5f79341a14..7676d73607 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -156,6 +156,7 @@
 		<li>[Fix] Smilies and images not viewed in topic-print view (Bug #47265 - Patch by nickvergessen)</li>
 		<li>[Fix] Force full date for PMs print-view (Patch by nickvergessen)</li>
 		<li>[Fix] Fix &quot;Always show a scrollbar for short pages&quot; for IE8 and Firefox 3.5 (Bug #47865 - Patch by stokerpiller)</li>
+		<li>[Fix] Do not allow setting group as default group for pending user (Bug #45675 - Patch by nickvergessen)</li>
 		<li>[Change] Change the data format of the default file ACM to be more secure from tampering and have better performance.</li>
 		<li>[Change] Add index on log_time to the log table to prevent slowdown on boards with many log entries. (Bug #44665 - Patch by bantu)</li>
 		<li>[Change] Template engine now permits to a limited extent variable includes.</li>
diff --git a/phpBB/includes/acp/acp_users.php b/phpBB/includes/acp/acp_users.php
index d8fef3f547..c27c259b46 100644
--- a/phpBB/includes/acp/acp_users.php
+++ b/phpBB/includes/acp/acp_users.php
@@ -2017,6 +2017,29 @@ class acp_users
 						}
 
 					break;
+
+					case 'approve':
+
+						if (confirm_box(true))
+						{
+							if (!$group_id)
+							{
+								trigger_error($user->lang['NO_GROUP'] . adm_back_link($this->u_action . '&amp;u=' . $user_id), E_USER_WARNING);
+							}
+							group_user_attributes($action, $group_id, $user_id);
+						}
+						else
+						{
+							confirm_box(false, $user->lang['CONFIRM_OPERATION'], build_hidden_fields(array(
+								'u'				=> $user_id,
+								'i'				=> $id,
+								'mode'			=> $mode,
+								'action'		=> $action,
+								'g'				=> $group_id))
+							);
+						}
+
+					break;
 				}
 
 				// Add user to group?
@@ -2109,10 +2132,12 @@ class acp_users
 							'U_DEFAULT'			=> $this->u_action . "&amp;action=default&amp;u=$user_id&amp;g=" . $data['group_id'],
 							'U_DEMOTE_PROMOTE'	=> $this->u_action . '&amp;action=' . (($data['group_leader']) ? 'demote' : 'promote') . "&amp;u=$user_id&amp;g=" . $data['group_id'],
 							'U_DELETE'			=> $this->u_action . "&amp;action=delete&amp;u=$user_id&amp;g=" . $data['group_id'],
+							'U_APPROVE'			=> ($group_type == 'pending') ? $this->u_action . "&amp;action=approve&amp;u=$user_id&amp;g=" . $data['group_id'] : '',
 
 							'GROUP_NAME'		=> ($group_type == 'special') ? $user->lang['G_' . $data['group_name']] : $data['group_name'],
 							'L_DEMOTE_PROMOTE'	=> ($data['group_leader']) ? $user->lang['GROUP_DEMOTE'] : $user->lang['GROUP_PROMOTE'],
 
+							'S_IS_MEMBER'		=> ($group_type != 'pending') ? true : false,
 							'S_NO_DEFAULT'		=> ($user_row['group_id'] != $data['group_id']) ? true : false,
 							'S_SPECIAL_GROUP'	=> ($group_type == 'special') ? true : false,
 							)
diff --git a/phpBB/includes/functions_user.php b/phpBB/includes/functions_user.php
index 4ea094e451..c69c27c9d7 100644
--- a/phpBB/includes/functions_user.php
+++ b/phpBB/includes/functions_user.php
@@ -3109,6 +3109,27 @@ function group_user_attributes($action, $group_id, $user_id_ary = false, $userna
 		break;
 
 		case 'default':
+			// We only set default group for approved members of the group
+			$sql = 'SELECT user_id
+				FROM ' . USER_GROUP_TABLE . "
+				WHERE group_id = $group_id
+					AND user_pending = 0
+					AND " . $db->sql_in_set('user_id', $user_id_ary);
+			$result = $db->sql_query($sql);
+
+			$user_id_ary = $username_ary = array();
+			while ($row = $db->sql_fetchrow($result))
+			{
+				$user_id_ary[] = $row['user_id'];
+			}
+			$db->sql_freeresult($result);
+
+			$result = user_get_id_name($user_id_ary, $username_ary);
+			if (!sizeof($user_id_ary) || $result !== false)
+			{
+				return 'NO_USERS';
+			}
+
 			$sql = 'SELECT user_id, group_id FROM ' . USERS_TABLE . '
 				WHERE ' . $db->sql_in_set('user_id', $user_id_ary, false, true);
 			$result = $db->sql_query($sql);
@@ -3197,7 +3218,7 @@ function group_validate_groupname($group_id, $group_name)
 */
 function group_set_user_default($group_id, $user_id_ary, $group_attributes = false, $update_listing = false)
 {
-	global $db;
+	global $cache, $db;
 
 	if (empty($user_id_ary))
 	{
@@ -3297,6 +3318,9 @@ function group_set_user_default($group_id, $user_id_ary, $group_attributes = fal
 	{
 		group_update_listings($group_id);
 	}
+
+	// Because some tables/caches use usercolour-specific data we need to purge this here.
+	$cache->destroy('sql', MODERATOR_CACHE_TABLE);
 }
 
 /**