diff --git a/.gitignore b/.gitignore
index 1d3956ea..4a291cec 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,7 @@ Gemfile.lock
 target
 .idea_modules
 .vagrant
+
+# The checksum is unique to each build, and we don't store builds in git.
+# Consequently, ignore the checksum file.
+resources/s3_website.jar.md5
diff --git a/bin/s3_website b/bin/s3_website
index 596e3bcc..d67098d3 100755
--- a/bin/s3_website
+++ b/bin/s3_website
@@ -2,6 +2,7 @@
 
 require File.expand_path(File.dirname(__FILE__)+ '/../lib/s3_website')
 require 'colored'
+require 'digest/md5'
 
 class Cfg < Thor
   desc 'create', 'Create a config file with placeholder values'
@@ -157,8 +158,18 @@ def resolve_jar(project_root, logger)
       File.exists? jar_path
     }.
     first
+  def jar_has_valid_checksum(jar_path, logger)
+    expected_checksum = File.read(File.dirname(__FILE__) + '/../resources/s3_website.jar.md5')
+    found_checksum = Digest::MD5.file(jar_path).hexdigest
+    if expected_checksum == found_checksum
+      true
+    else
+      logger.info_msg "The jar file has invalid checksum. Expected #{expected_checksum} but got #{found_checksum}"
+      false
+    end
+  end
   jar_file =
-    if found_jar
+    if found_jar and jar_has_valid_checksum(found_jar, logger)
       found_jar
     else
       is_development = File.exists?(project_root + '/.git')
diff --git a/changelog.md b/changelog.md
index aa03f2fa..95930309 100644
--- a/changelog.md
+++ b/changelog.md
@@ -2,6 +2,10 @@
 
 This project uses [Semantic Versioning](http://semver.org).
 
+## 2.1.1
+
+* Verify that the s3_website.jar is not corrupted. Download it again, if it is.
+
 ## 2.1.0
 
 * Show the upload reason when calling `push --verbose`
diff --git a/lib/s3_website/version.rb b/lib/s3_website/version.rb
index 39eb9893..e6a2f5b5 100644
--- a/lib/s3_website/version.rb
+++ b/lib/s3_website/version.rb
@@ -1,3 +1,3 @@
 module S3Website
-  VERSION = '2.1.0'
+  VERSION = '2.1.1'
 end
diff --git a/release b/release
index 81b52678..7070ffbd 100755
--- a/release
+++ b/release
@@ -16,9 +16,14 @@ def run(cmd)
 end
 
 puts "Building s3_website.jar..."
+jar_location = 'target/scala-2.11/s3_website.jar'
 run "./sbt clean"
 run "./sbt assembly"
 
+# The bin s3_website uses the MD5 checksum to verify that the jar is not corrupted
+jar_md5 = Digest::MD5.file(jar_location).hexdigest
+File.write('resources/s3_website.jar.md5', jar_md5)
+
 tag_name = "v#{version}"
 run "git tag #{tag_name} && git push origin #{tag_name}"
 run "git push"
@@ -32,5 +37,5 @@ release = client.create_release(
   :body => "See https://github.com/laurilehmijoki/s3_website/blob/master/changelog.md##{version.gsub('.', '')}"
 )
 puts "Uploading s3_website.jar..."
-client.upload_asset(release[:url], 'target/scala-2.11/s3_website.jar')
+client.upload_asset(release[:url], jar_location)
 run "gem push pkg/s3_website-#{version}.gem"
diff --git a/s3_website.gemspec b/s3_website.gemspec
index eb4b56f6..9df7c83c 100644
--- a/s3_website.gemspec
+++ b/s3_website.gemspec
@@ -25,7 +25,12 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rake', '10.1.1'
   s.add_development_dependency 'octokit', '3.1.0'
 
-  s.files         = `git ls-files`.split("\n").reject { |f| f.match('sbt-launch.jar') }
+  s.files         = `git ls-files`
+                      .split("\n")
+                      # Reject the SBT jar, as it is a big file.
+                      .reject { |f| f.match('sbt-launch.jar') }
+                      # Include the checksum file in the gem:
+                      .push('resources/s3_website.jar.md5')
   s.test_files    = `git ls-files -- src/test/*`.split("\n")
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ["lib"]