diff --git a/md_simple_editor.gemspec b/md_simple_editor.gemspec
index 49a65b9..c677ec1 100644
--- a/md_simple_editor.gemspec
+++ b/md_simple_editor.gemspec
@@ -21,5 +21,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "bundler", "~> 1.3"
   spec.add_development_dependency "rake"
 
-  spec.add_dependency "font-awesome-rails"
+  spec.add_runtime_dependency "font-awesome-rails", "~> 4.0.3.1"
 end