diff --git a/Gifu.podspec b/Gifu.podspec
index 58c7b99..27eebb8 100644
--- a/Gifu.podspec
+++ b/Gifu.podspec
@@ -9,6 +9,7 @@ Pod::Spec.new do |s|
   s.source = { :git => "https://github.com/kaishin/Gifu.git", :tag => "v#{s.version}", :submodules => true }
   s.platform = :ios, "9.0"
   s.platform = :tvos, "9.0"
+  s.swift_version = "4.2"
   s.ios.source_files = "Source/**/*.{h,swift}"
   s.tvos.source_files = "Source/**/*.{h,swift}"
   s.ios.deployment_target = "9.0"