diff --git a/CountdownLabel.podspec b/CountdownLabel.podspec
index 54c66f0..c31d933 100644
--- a/CountdownLabel.podspec
+++ b/CountdownLabel.podspec
@@ -1,12 +1,12 @@
 Pod::Spec.new do |s|
   s.name         = "CountdownLabel"
-  s.version      = '4.0.1'
+  s.version      = '5.0.0'
   s.summary      = 'Simple countdown UILabel with morphing animation, and some useful function.'
   s.homepage     = "https://github.com/suzuki-0000/CountdownLabel"
   s.license      = { :type => "MIT", :file => "LICENSE" }
   s.author       = { "suzuki_keishi" => "keishi.1983@gmail.com" }
   s.source       = { :git => "https://github.com/suzuki-0000/CountdownLabel.git", :tag => s.version }
-  s.platform     = :ios, "8.2"
+  s.platform     = :ios, "10.0"
   s.source_files = 'CountdownLabel/*.swift'
   s.source_files = 'CountdownLabel/**/*.swift'
   s.requires_arc = true
diff --git a/CountdownLabel/CountdownLabel.swift b/CountdownLabel/CountdownLabel.swift
index 7314dab..f5153bb 100644
--- a/CountdownLabel/CountdownLabel.swift
+++ b/CountdownLabel/CountdownLabel.swift
@@ -33,7 +33,7 @@ public class CountdownLabel: LTMorphingLabel {
     public var dateFormatter: DateFormatter {
         let df = DateFormatter()
         df.locale = Locale(identifier: "en_US_POSIX")
-        df.timeZone = NSTimeZone(name: "GMT") as TimeZone!
+        df.timeZone = NSTimeZone(name: "GMT") as TimeZone?
         df.dateFormat = timeFormat
         return df
     }