diff --git a/.swift-version b/.swift-version
index cb2b00e4..8c50098d 100644
--- a/.swift-version
+++ b/.swift-version
@@ -1 +1 @@
-3.0.1
+3.1
diff --git a/.travis.yml b/.travis.yml
index 1d6699ff..ddb9164c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,7 +6,7 @@ matrix:
   include:
     - os: osx
       language: objective-c
-      osx_image: xcode8.1
+      osx_image: xcode8.3
       script:
         - set -o pipefail
         - xcodebuild build-for-testing test-without-building -workspace APIKit.xcworkspace -scheme APIKit -configuration Release ENABLE_TESTABILITY=YES | xcpretty -c
@@ -16,7 +16,7 @@ matrix:
         - bash <(curl -s https://codecov.io/bash)
     - os: osx
       language: generic
-      osx_image: xcode8.1
+      osx_image: xcode8.3
       script:
         - swift build
         - swift test
diff --git a/README.md b/README.md
index 2ffdf892..6dd793e3 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ APIKit
 [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 [![Version](https://img.shields.io/cocoapods/v/APIKit.svg?style=flat)](http://cocoadocs.org/docsets/APIKit)
 [![Platform](https://img.shields.io/cocoapods/p/APIKit.svg?style=flat)](http://cocoadocs.org/docsets/APIKit)
-
+[![Swift Package Manager](https://img.shields.io/badge/Swift%20Package%20Manager-compatible-brightgreen.svg)](https://github.com/apple/swift-package-manager)
 
 APIKit is a type-safe networking abstraction layer that associates request type with response type.
 
@@ -30,7 +30,7 @@ Session.send(request) { result in
 
 ## Requirements
 
-- Swift 3.0
+- Swift 3.0 or later
 - iOS 8.0 or later
 - Mac OS 10.10 or later
 - watchOS 2.0 or later
@@ -42,13 +42,13 @@ If you use Swift 2.2 or 2.3, try [APIKit 2.0.5](https://github.com/ishkawa/APIKi
 
 #### [Carthage](https://github.com/Carthage/Carthage)
 
-- Insert `github "ishkawa/APIKit" ~> 3.0` to your Cartfile.
+- Insert `github "ishkawa/APIKit" ~> 3.1` to your Cartfile.
 - Run `carthage update`.
 - Link your app with `APIKit.framework` and `Result.framework` in `Carthage/Build`.
 
 #### [CocoaPods](https://github.com/cocoapods/cocoapods)
 
-- Insert `pod 'APIKit', '~> 3.0'` to your Podfile.
+- Insert `pod 'APIKit', '~> 3.1'` to your Podfile.
 - Run `pod install`.
 
 Note: CocoaPods 1.1.0 is required to install APIKit 3.
diff --git a/Sources/APIKit/BodyParameters/MultipartFormDataBodyParameters.swift b/Sources/APIKit/BodyParameters/MultipartFormDataBodyParameters.swift
index 26947598..3253c6d8 100644
--- a/Sources/APIKit/BodyParameters/MultipartFormDataBodyParameters.swift
+++ b/Sources/APIKit/BodyParameters/MultipartFormDataBodyParameters.swift
@@ -18,7 +18,7 @@ import Foundation
 public struct MultipartFormDataBodyParameters: BodyParameters {
     /// `EntityType` represents wheather the entity is expressed as `Data` or `InputStream`.
     public enum EntityType {
-        /// Expresses the entity as `Data`, which has faster upload speed and lager memory usage.
+        /// Expresses the entity as `Data`, which has faster upload speed and larger memory usage.
         case data
 
         /// Expresses the entity as `InputStream`, which has smaller memory usage and slower upload speed.
@@ -86,7 +86,7 @@ public extension MultipartFormDataBodyParameters {
             self.count = data.count
         }
 
-        /// Returns Part instance that has input stream of specifed data.
+        /// Returns Part instance that has input stream of specified data.
         /// If `mimeType` or `fileName` are `nil`, the fields will be omitted.
         public init(data: Data, name: String, mimeType: String? = nil, fileName: String? = nil) {
             self.inputStream = InputStream(data: data)
@@ -96,7 +96,7 @@ public extension MultipartFormDataBodyParameters {
             self.count = data.count
         }
 
-        /// Returns Part instance that has input stream of specifed file URL.
+        /// Returns Part instance that has input stream of specified file URL.
         /// If `mimeType` or `fileName` are `nil`, values for the fields will be detected from URL.
         public init(fileURL: URL, name: String, mimeType: String? = nil, fileName: String? = nil) throws {
             guard let inputStream = InputStream(url: fileURL) else {