diff --git a/Source/WebSocket.swift b/Source/WebSocket.swift
index 8b6d02ae..ca1d9a3f 100644
--- a/Source/WebSocket.swift
+++ b/Source/WebSocket.swift
@@ -388,9 +388,9 @@ public class WebSocket : NSObject, StreamDelegate {
      */
     public func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
         if let sec = security, !certValidated && [.hasBytesAvailable, .hasSpaceAvailable].contains(eventCode) {
-            let trust = aStream.property(forKey: kCFStreamPropertySSLPeerTrust as Stream.PropertyKey) as AnyObject
+            let trust = aStream.property(forKey: kCFStreamPropertySSLPeerTrust as Stream.PropertyKey) as! SecTrust
             let domain = aStream.property(forKey: kCFStreamSSLPeerName as Stream.PropertyKey) as? String
-            if sec.isValid(trust as! SecTrust, domain: domain) {
+            if sec.isValid(trust, domain: domain) {
                 certValidated = true
             } else {
                 let error = errorWithDetail("Invalid SSL certificate", code: 1)