diff --git a/omniauth-oauth2.gemspec b/omniauth-oauth2.gemspec
index 6270d5a..a3f7407 100644
--- a/omniauth-oauth2.gemspec
+++ b/omniauth-oauth2.gemspec
@@ -4,7 +4,7 @@ require "omniauth-oauth2/version"
 
 Gem::Specification.new do |gem|
   gem.add_dependency "oauth2",     [">= 1.4", "< 3"]
-  gem.add_dependency "omniauth",   [">= 1.9", "< 3"]
+  gem.add_dependency "omniauth",   "~> 2.0"
 
   gem.add_development_dependency "bundler", "~> 2.0"