diff --git a/Sources/Base64.swift b/Sources/Base64.swift
index 32b18cf..9bb73ed 100644
--- a/Sources/Base64.swift
+++ b/Sources/Base64.swift
@@ -4,7 +4,10 @@ import Foundation
 /// URI Safe base64 encode
 func base64encode(_ input:Data) -> String {
   let data = input.base64EncodedData(options: NSData.Base64EncodingOptions(rawValue: 0))
-  let string = NSString(data: data, encoding: String.Encoding.utf8.rawValue) as! String
+  guard let cocoaString = NSString(data: data, encoding: String.Encoding.utf8.rawValue) else {
+    return ""
+  }
+  let string = String(describing: cocoaString)
   return string
     .replacingOccurrences(of: "+", with: "-", options: NSString.CompareOptions(rawValue: 0), range: nil)
     .replacingOccurrences(of: "/", with: "_", options: NSString.CompareOptions(rawValue: 0), range: nil)
@@ -14,15 +17,15 @@ func base64encode(_ input:Data) -> String {
 /// URI Safe base64 decode
 func base64decode(_ input:String) -> Data? {
   let rem = input.characters.count % 4
-
+  
   var ending = ""
   if rem > 0 {
     let amount = 4 - rem
     ending = String(repeating: "=", count: amount)
   }
-
+  
   let base64 = input.replacingOccurrences(of: "-", with: "+", options: NSString.CompareOptions(rawValue: 0), range: nil)
     .replacingOccurrences(of: "_", with: "/", options: NSString.CompareOptions(rawValue: 0), range: nil) + ending
-
+  
   return Data(base64Encoded: base64, options: NSData.Base64DecodingOptions(rawValue: 0))
 }
diff --git a/Sources/JWT.swift b/Sources/JWT.swift
index 84f4809..078957f 100644
--- a/Sources/JWT.swift
+++ b/Sources/JWT.swift
@@ -81,7 +81,7 @@ public func encode(_ payload:Payload, algorithm:Algorithm) -> String {
     return nil
   }
 
-  let header = encodeJSON(["typ": "JWT" as AnyObject, "alg": algorithm.description as AnyObject])!
+  let header = encodeJSON(["typ": "JWT", "alg": algorithm.description])!
   let payload = encodeJSON(payload)!
   let signingInput = "\(header).\(payload)"
   let signature = algorithm.sign(signingInput)
@@ -96,7 +96,7 @@ open class PayloadBuilder {
       return payload["iss"] as? String
     }
     set {
-      payload["iss"] = newValue as AnyObject?
+      payload["iss"] = newValue
     }
   }
 
@@ -105,7 +105,7 @@ open class PayloadBuilder {
       return payload["aud"] as? String
     }
     set {
-      payload["aud"] = newValue as AnyObject?
+      payload["aud"] = newValue
     }
   }
 
@@ -118,7 +118,7 @@ open class PayloadBuilder {
       return nil
     }
     set {
-      payload["exp"] = newValue?.timeIntervalSince1970 as AnyObject?
+      payload["exp"] = newValue?.timeIntervalSince1970
     }
   }
 
@@ -131,7 +131,7 @@ open class PayloadBuilder {
       return nil
     }
     set {
-      payload["nbf"] = newValue?.timeIntervalSince1970 as AnyObject?
+      payload["nbf"] = newValue?.timeIntervalSince1970
     }
   }
 
@@ -144,7 +144,7 @@ open class PayloadBuilder {
       return nil
     }
     set {
-      payload["iat"] = newValue?.timeIntervalSince1970 as AnyObject?
+      payload["iat"] = newValue?.timeIntervalSince1970
     }
   }