diff --git a/Source/SocketAckManager.swift b/Source/SocketAckManager.swift
index c32dc04..c00797a 100644
--- a/Source/SocketAckManager.swift
+++ b/Source/SocketAckManager.swift
@@ -35,7 +35,7 @@ private struct SocketAck : Hashable {
         self.ack = ack
     }
     
-    init(ack: Int, callback: AckCallback) {
+    init(ack: Int, callback: @escaping AckCallback) {
         self.ack = ack
         self.callback = callback
     }
@@ -52,7 +52,7 @@ private func ==(lhs: SocketAck, rhs: SocketAck) -> Bool {
 struct SocketAckManager {
     private var acks = Set<SocketAck>(minimumCapacity: 1)
     
-    mutating func addAck(_ ack: Int, callback: AckCallback) {
+    mutating func addAck(_ ack: Int, callback: @escaping AckCallback) {
         acks.insert(SocketAck(ack: ack, callback: callback))
     }
     
diff --git a/Source/SocketIOClient.swift b/Source/SocketIOClient.swift
index 156baee..22a5e88 100644
--- a/Source/SocketIOClient.swift
+++ b/Source/SocketIOClient.swift
@@ -356,7 +356,7 @@ public final class SocketIOClient : NSObject, SocketEngineClient, SocketParsable
     /// Adds a handler for an event.
     /// Returns: A unique id for the handler
     @discardableResult
-    public func on(_ event: String, callback: NormalCallback) -> UUID {
+    public func on(_ event: String, callback: @escaping NormalCallback) -> UUID {
         DefaultSocketLogger.Logger.log("Adding handler for event: %@", type: logType, args: event)
 
         let handler = SocketEventHandler(event: event, id: UUID(), callback: callback)
@@ -368,7 +368,7 @@ public final class SocketIOClient : NSObject, SocketEngineClient, SocketParsable
     /// Adds a single-use handler for an event.
     /// Returns: A unique id for the handler
     @discardableResult
-    public func once(_ event: String, callback: NormalCallback) -> UUID {
+    public func once(_ event: String, callback: @escaping NormalCallback) -> UUID {
         DefaultSocketLogger.Logger.log("Adding once handler for event: %@", type: logType, args: event)
 
         let id = UUID()
diff --git a/Source/SocketTypes.swift b/Source/SocketTypes.swift
index b2f04e0..25cb8f7 100644
--- a/Source/SocketTypes.swift
+++ b/Source/SocketTypes.swift
@@ -41,7 +41,7 @@ extension String : SocketData {}
 
 public typealias AckCallback = ([AnyObject]) -> Void
 public typealias NormalCallback = ([AnyObject], SocketAckEmitter) -> Void
-public typealias OnAckCallback = (_ timeoutAfter: UInt64, _ callback: AckCallback) -> Void
+public typealias OnAckCallback = (_ timeoutAfter: UInt64, _ callback: @escaping AckCallback) -> Void
 
 typealias Probe = (msg: String, type: SocketEnginePacketType, data: [Data])
 typealias ProbeWaitQueue = [Probe]