diff --git a/README.md b/README.md
index 80234b1..9c29b6a 100644
--- a/README.md
+++ b/README.md
@@ -143,6 +143,8 @@ Methods
 11. `reconnect()` - Causes the client to reconnect to the server.
 12. `joinNamespace()` - Causes the client to join nsp. Shouldn't need to be called unless you change nsp manually.
 13. `leaveNamespace()` - Causes the client to leave the nsp and go back to /
+14. `once(event: String, callback: NormalCallback)` - Adds a handler that will only be executed once.
+15. `once(event event: String, callback: NormalCallbackObjectiveC)` - Adds a handler that will only be executed once.
 
 Client Events
 ------
diff --git a/SocketIOClientSwift/SocketEventHandler.swift b/SocketIOClientSwift/SocketEventHandler.swift
index c61c4c5..beb88a6 100644
--- a/SocketIOClientSwift/SocketEventHandler.swift
+++ b/SocketIOClientSwift/SocketEventHandler.swift
@@ -35,19 +35,21 @@ private func emitAckCallbackObjectiveC(socket: SocketIOClient?, num: Int?)
 }
 
 struct SocketEventHandler {
-    let id = NSUUID()
     let event: String
+    let id: NSUUID
     let callback: NormalCallback?
     let callBackObjectiveC: NormalCallbackObjectiveC?
     
-    init(event: String, callback: NormalCallback) {
+    init(event: String, id: NSUUID = NSUUID(), callback: NormalCallback) {
         self.event = event
+        self.id = id
         self.callback = callback
         self.callBackObjectiveC = nil
     }
     
-    init(event: String, callback: NormalCallbackObjectiveC) {
+    init(event: String, id: NSUUID = NSUUID(), callback: NormalCallbackObjectiveC) {
         self.event = event
+        self.id = id
         self.callback = nil
         self.callBackObjectiveC = callback
     }
diff --git a/SocketIOClientSwift/SocketIOClient.swift b/SocketIOClientSwift/SocketIOClient.swift
index c9fdad0..00b328a 100644
--- a/SocketIOClientSwift/SocketIOClient.swift
+++ b/SocketIOClientSwift/SocketIOClient.swift
@@ -430,14 +430,15 @@ public final class SocketIOClient: NSObject, SocketEngineClient {
     public func once(event: String, callback: NormalCallback) {
         Logger.log("Adding once handler for event: %@", type: logType, args: event)
         
-        var handler: SocketEventHandler?;
-
-        handler = SocketEventHandler(event: event) { (data, ack: AckEmitter?) in
-            self.handlers = ContiguousArray(self.handlers.filter { $0.id != handler!.id })
+        let id = NSUUID()
+        
+        let handler = SocketEventHandler(event: event, id: id) {[weak self] (data, ack: AckEmitter?) in
+            guard let this = self else {return}
+            this.handlers = ContiguousArray(this.handlers.filter {$0.id != id})
             callback(data, ack)
         }
 
-        handlers.append(handler!)
+        handlers.append(handler)
     }
     
     /**
@@ -446,14 +447,15 @@ public final class SocketIOClient: NSObject, SocketEngineClient {
     public func once(event event: String, callback: NormalCallbackObjectiveC) {
         Logger.log("Adding once handler for event: %@", type: logType, args: event)
         
-        var handler: SocketEventHandler?;
-
-        handler = SocketEventHandler(event: event) { (data, ack: AckEmitterObjectiveC?) in
-            self.handlers = ContiguousArray(self.handlers.filter { $0.id != handler!.id })
+        let id = NSUUID()
+        
+        let handler = SocketEventHandler(event: event, id: id) {[weak self] (data, ack: AckEmitterObjectiveC?) in
+            guard let this = self else {return}
+            this.handlers = ContiguousArray(this.handlers.filter {$0.id != id})
             callback(data, ack)
         }
-
-        handlers.append(handler!)
+        
+        handlers.append(handler)
     }
     
     /**