diff --git a/Yep/Extensions/String+Yep.swift b/Yep/Extensions/String+Yep.swift
index d0623b6d..6d7d1ec5 100644
--- a/Yep/Extensions/String+Yep.swift
+++ b/Yep/Extensions/String+Yep.swift
@@ -20,6 +20,9 @@ extension String {
             return nil
         }
     }
+}
+
+extension String {
 
     enum TrimmingType {
         case Whitespace
@@ -34,4 +37,51 @@ extension String {
             return stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
         }
     }
-}
\ No newline at end of file
+}
+
+extension String {
+
+    func yep_mentionWordInIndex(index: Int) -> (wordString: String, mentionWordRange: Range<Index>)? {
+
+        guard index > 0 else {
+            return nil
+        }
+
+        let index = startIndex.advancedBy(index)
+
+        var wordString: String?
+        var wordRange: Range<Index>?
+
+        self.enumerateSubstringsInRange(Range<Index>(start: startIndex, end: endIndex), options: [.ByWords, .Reverse]) { (substring, substringRange, enclosingRange, stop) -> () in
+
+            //println("substring: \(substring)")
+            //println("substringRange: \(substringRange)")
+            //println("enclosingRange: \(enclosingRange)")
+
+            if substringRange.contains(index) {
+                wordString = substring
+                wordRange = substringRange
+                stop = true
+            }
+        }
+
+        guard let _wordString = wordString, _wordRange = wordRange else {
+            return nil
+        }
+
+        guard _wordRange.startIndex != startIndex else {
+            return nil
+        }
+
+        let mentionWordRange = Range<Index>(start: _wordRange.startIndex.advancedBy(-1), end: _wordRange.endIndex)
+
+        let mentionWord = substringWithRange(mentionWordRange)
+
+        guard mentionWord.hasPrefix("@") else {
+            return nil
+        }
+
+        return (_wordString, mentionWordRange)
+    }
+}
+
diff --git a/Yep/Services/YepService.swift b/Yep/Services/YepService.swift
index c3aa60d1..61e52588 100644
--- a/Yep/Services/YepService.swift
+++ b/Yep/Services/YepService.swift
@@ -3695,7 +3695,7 @@ struct UsernamePrefixMatchedUser {
     let userID: String
     let username: String
     let nickname: String
-    let avatarURLString: String
+    let avatarURLString: String?
 
     var mentionUsername: String {
         return "@" + username
@@ -3709,7 +3709,7 @@ func usersMatchWithUsernamePrefix(usernamePrefix: String, failureHandler: ((Reas
     ]
 
     let parse: JSONDictionary -> [UsernamePrefixMatchedUser]? = { data in
-        //println("usersMatchWithUsernamePrefix: \(data)")
+        println("usersMatchWithUsernamePrefix: \(data)")
 
         if let usersData = data["users"] as? [JSONDictionary] {
             let users: [UsernamePrefixMatchedUser] = usersData.map({ userInfo in
@@ -3717,12 +3717,14 @@ func usersMatchWithUsernamePrefix(usernamePrefix: String, failureHandler: ((Reas
                     userID = userInfo["id"] as? String,
                     username = userInfo["username"] as? String,
                     nickname = userInfo["nickname"] as? String,
-                    avatarInfo = userInfo["avatar"] as? JSONDictionary,
-                    avatarURLString = avatarInfo["thumb_url"] as? String
+                    avatarInfo = userInfo["avatar"] as? JSONDictionary
+                    //avatarURLString = avatarInfo["thumb_url"] as? String
                 else {
                     return nil
                 }
 
+                let avatarURLString = avatarInfo["thumb_url"] as? String
+
                 return UsernamePrefixMatchedUser(userID: userID, username: username, nickname: nickname, avatarURLString: avatarURLString)
             }).flatMap({ $0 })
 
diff --git a/Yep/Views/Mention/MentionView.swift b/Yep/Views/Mention/MentionView.swift
index 3aca2d11..248fa3da 100644
--- a/Yep/Views/Mention/MentionView.swift
+++ b/Yep/Views/Mention/MentionView.swift
@@ -72,8 +72,12 @@ private class MentionUserCell: UITableViewCell {
 
     func configureWithUsernamePrefixMatchedUser(user: UsernamePrefixMatchedUser) {
 
-        let plainAvatar = PlainAvatar(avatarURLString: user.avatarURLString, avatarStyle: picoAvatarStyle)
+        if let avatarURLString = user.avatarURLString {
+        let plainAvatar = PlainAvatar(avatarURLString: avatarURLString, avatarStyle: picoAvatarStyle)
         avatarImageView.navi_setAvatar(plainAvatar, withFadeTransitionDuration: avatarFadeTransitionDuration)
+        } else {
+            avatarImageView.image = UIImage(named: "default_avatar_30")
+        }
 
         nicknameLabel.text = user.nickname
         mentionUsernameLabel.text = user.mentionUsername
@@ -105,6 +109,7 @@ class MentionView: UIView {
         let tableView = UITableView()
 
         tableView.backgroundColor = UIColor.clearColor()
+        tableView.separatorInset = UIEdgeInsets(top: 0, left: 60, bottom: 0, right: 0)
 
         let effect = UIBlurEffect(style: .ExtraLight)
 
diff --git a/Yep/Views/MessageToolbar/MessageToolbar.swift b/Yep/Views/MessageToolbar/MessageToolbar.swift
index 7338be81..314af2e5 100644
--- a/Yep/Views/MessageToolbar/MessageToolbar.swift
+++ b/Yep/Views/MessageToolbar/MessageToolbar.swift
@@ -441,6 +441,8 @@ class MessageToolbar: UIToolbar {
             text.replaceRange(range, with: mentionUsernameWithSpaceSuffix)
 
             messageTextView.text = text
+
+            updateHeightOfMessageTextView()
         }
     }
 
@@ -490,19 +492,16 @@ extension MessageToolbar: UITextViewDelegate {
             state = text.isEmpty ? .BeginTextInput : .TextInputing
 
             if needDetectMention {
-                let parts = text.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
 
-                if let lastPart = parts.last {
-                    if lastPart.hasPrefix("@") {
-                        let usernamePrefix = lastPart.substringFromIndex(lastPart.startIndex.advancedBy(1))
+                let currentLetterIndex = textView.selectedRange.location - 1
 
-                        if !usernamePrefix.isEmpty {
-                            mentionUsernameRange = text.rangeOfString(lastPart)
-                            tryMentionUserAction?(usernamePrefix: usernamePrefix)
+                if let (wordString, mentionWordRange) = text.yep_mentionWordInIndex(currentLetterIndex) {
+                    //println("mentionWord: \(wordString), \(mentionWordRange)")
 
-                            return
-                        }
-                    }
+                    mentionUsernameRange = mentionWordRange
+                    tryMentionUserAction?(usernamePrefix: wordString)
+
+                    return
                 }
 
                 giveUpMentionUserAction?()