diff --git a/Source/SocketIO/Engine/SocketEngine.swift b/Source/SocketIO/Engine/SocketEngine.swift
index 4904ee5..bca0944 100644
--- a/Source/SocketIO/Engine/SocketEngine.swift
+++ b/Source/SocketIO/Engine/SocketEngine.swift
@@ -359,6 +359,7 @@ open class SocketEngine : NSObject, URLSessionDelegate, SocketEnginePollable, So
     ///
     /// **You shouldn't call this directly**
     open func doFastUpgrade() {
+        
         if waitingForPoll {
             DefaultSocketLogger.Logger.error("Outstanding poll when switched to WebSockets," +
                 "we'll probably disconnect soon. You should report this.", type: SocketEngine.logType)
@@ -371,6 +372,12 @@ open class SocketEngine : NSObject, URLSessionDelegate, SocketEnginePollable, So
         fastUpgrade = false
         probing = false
         flushProbeWait()
+        
+        // Need to flush postWait to socket since it connected successfully
+        // (moved from flushProbeWait() since it is also called on connected failure)
+        if !postWait.isEmpty {
+            flushWaitingForPostToWebSocket()
+        }
     }
 
     private func flushProbeWait() {
@@ -381,10 +388,6 @@ open class SocketEngine : NSObject, URLSessionDelegate, SocketEnginePollable, So
         }
 
         probeWait.removeAll(keepingCapacity: false)
-
-        if postWait.count != 0 {
-            flushWaitingForPostToWebSocket()
-        }
     }
 
     /// Causes any packets that were waiting for POSTing to be sent through the WebSocket. This happens because when
diff --git a/Source/SocketIO/Manager/SocketManager.swift b/Source/SocketIO/Manager/SocketManager.swift
index 7434ec7..830bf93 100644
--- a/Source/SocketIO/Manager/SocketManager.swift
+++ b/Source/SocketIO/Manager/SocketManager.swift
@@ -168,7 +168,11 @@ open class SocketManager : NSObject, SocketManagerSpec, SocketParsable, SocketDa
         DefaultSocketLogger.Logger.log("Adding engine", type: SocketManager.logType)
 
         engine?.engineQueue.sync {
+            
             self.engine?.client = nil
+            
+            // Close old engine so it will not leak because of URLSession if in polling mode
+            self.engine?.disconnect(reason: "Adding new engine")
         }
 
         engine = SocketEngine(client: self, url: socketURL, config: config)