diff --git a/README.md b/README.md
index 4290ab9..54f1347 100644
--- a/README.md
+++ b/README.md
@@ -4,11 +4,11 @@ Download any website from the Internet Archive Wayback Machine.
 
 ## Installation
 
-You need to install Ruby on your system - if you don't already have it, then run:
+You need to install Ruby on your system (>= 1.9.2) - if you don't already have it, then run:
 
     gem install wayback_machine_downloader
 
-## Usage 
+## Usage
 
 ### Basic
 
diff --git a/wayback_machine_downloader.gemspec b/wayback_machine_downloader.gemspec
index 848e668..7cb1fb4 100644
--- a/wayback_machine_downloader.gemspec
+++ b/wayback_machine_downloader.gemspec
@@ -11,6 +11,7 @@ Gem::Specification.new do |s|
   s.files       = ["lib/wayback_machine_downloader.rb"]
   s.homepage    = "https://github.com/hartator/wayback_machine_downloader"
   s.license     = "MIT"
+  s.required_ruby_version = '>= 1.9.2'
   s.add_development_dependency 'pry-rescue', '~> 1.4'
   s.add_development_dependency 'pry-stack_explorer', '~> 0.4'
 end