diff --git a/program/include/rcube_imap.php b/program/include/rcube_imap.php
index d08554206..028d998c3 100644
--- a/program/include/rcube_imap.php
+++ b/program/include/rcube_imap.php
@@ -2474,8 +2474,7 @@ class rcube_imap
         }
 
         // move messages
-        $move = $this->conn->move($uids, $from_mbox, $to_mbox);
-        $moved = !($move === false || $move < 0);
+        $moved = $this->conn->move($uids, $from_mbox, $to_mbox);
 
         // send expunge command in order to have the moved message
         // really deleted from the source mailbox
@@ -2536,8 +2535,9 @@ class rcube_imap
         list($uids, $all_mode) = $this->_parse_uids($uids, $from_mbox);
 
         // exit if no message uids are specified
-        if (empty($uids))
+        if (empty($uids)) {
             return false;
+        }
 
         // make sure mailbox exists
         if ($to_mbox != 'INBOX' && !$this->mailbox_exists($tbox, true)) {
@@ -2548,8 +2548,7 @@ class rcube_imap
         }
 
         // copy messages
-        $copy = $this->conn->copy($uids, $from_mbox, $to_mbox);
-        $copied = !($copy === false || $copy < 0);
+        $copied = $this->conn->copy($uids, $from_mbox, $to_mbox);
 
         if ($copied) {
             $this->_clear_messagecount($to_mbox);
@@ -3650,7 +3649,7 @@ class rcube_imap
         if (!$msg_count)
             return $cache_count ? -2 : 1;
 
-        if ($cache_count==$msg_count) {
+        if ($cache_count == $msg_count) {
             if ($this->skip_deleted) {
 	            $h_index = $this->conn->fetchHeaderIndex($mailbox, "1:*", 'UID', $this->skip_deleted);
 
diff --git a/program/include/rcube_imap_generic.php b/program/include/rcube_imap_generic.php
index e9a5a2d44..5d16dc0c1 100644
--- a/program/include/rcube_imap_generic.php
+++ b/program/include/rcube_imap_generic.php
@@ -1199,35 +1199,52 @@ class rcube_imap_generic
 	    return implode(',', $result);
     }
 
-    function UID2ID($folder, $uid)
+    /**
+     * Returns message sequence identifier
+     *
+     * @param string $mailbox Mailbox name
+     * @param int    $uid     Message unique identifier (UID)
+     *
+     * @return int Message sequence identifier
+     * @access public
+     */
+    function UID2ID($mailbox, $uid)
     {
 	    if ($uid > 0) {
-    		$id_a = $this->search($folder, "UID $uid");
+    		$id_a = $this->search($mailbox, "UID $uid");
 	    	if (is_array($id_a) && count($id_a) == 1) {
-		    	return $id_a[0];
+		    	return (int) $id_a[0];
 		    }
 	    }
-	    return false;
+	    return null;
     }
 
-    function ID2UID($folder, $id)
+    /**
+     * Returns message unique identifier (UID)
+     *
+     * @param string $mailbox Mailbox name
+     * @param int    $uid     Message sequence identifier
+     *
+     * @return int Message unique identifier
+     * @access public
+     */
+    function ID2UID($mailbox, $id)
     {
-	    if (empty($id)) {
-	        return 	-1;
+	    if (empty($id) || $id < 0) {
+	        return 	null;
 	    }
 
     	if (!$this->select($folder)) {
-            return -1;
+            return null;
         }
 
-	    $result  = -1;
         list($code, $response) = $this->execute('FETCH', array($id, '(UID)'));
 
         if ($code == self::ERROR_OK && preg_match("/^\* $id FETCH \(UID (.*)\)/i", $response, $m)) {
-			$result = $m[1];
+			return (int) $m[1];
         }
 
-    	return $result;
+    	return null;
     }
 
     function fetchUIDs($mailbox, $message_set=null)
@@ -1615,18 +1632,32 @@ class rcube_imap_generic
     function copy($messages, $from, $to)
     {
 	    if (empty($from) || empty($to)) {
-	        return -1;
+	        return false;
 	    }
 
 	    if (!$this->select($from)) {
-            return -1;
+	        return false;
 	    }
 
         $result = $this->execute('UID COPY', array(
             $this->compressMessageSet($messages), $this->escape($to)),
             self::COMMAND_NORESPONSE);
 
-	    return $result;
+	    return ($result == self::ERROR_OK);
+    }
+
+    function move($messages, $from, $to)
+    {
+        if (!$from || !$to) {
+            return false;
+        }
+
+        $r = $this->copy($messages, $from, $to);
+
+        if ($r) {
+            return $this->delete($from, $messages);
+        }
+        return $r;
     }
 
     // Don't be tempted to change $str to pass by reference to speed this up - it will slow it down by about
@@ -1806,20 +1837,6 @@ class rcube_imap_generic
 	    return false;
     }
 
-    function move($messages, $from, $to)
-    {
-        if (!$from || !$to) {
-            return -1;
-        }
-
-        $r = $this->copy($messages, $from, $to);
-
-        if ($r==0) {
-            return $this->delete($from, $messages);
-        }
-        return $r;
-    }
-
     /**
      * Returns list of mailboxes
      *