diff --git a/two_factor_authentication.gemspec b/two_factor_authentication.gemspec
index a5b886d..a95b2ed 100644
--- a/two_factor_authentication.gemspec
+++ b/two_factor_authentication.gemspec
@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'rails', '>= 3.1.1'
   s.add_runtime_dependency 'devise'
   s.add_runtime_dependency 'randexp'
-  s.add_runtime_dependency 'rotp', '>= 3.2.0'
+  s.add_runtime_dependency 'rotp', '>= 4.0.0'
   s.add_runtime_dependency 'encryptor'
 
   s.add_development_dependency 'bundler'