diff --git a/rails-pg-adapter.gemspec b/rails-pg-adapter.gemspec
index f716e69..974ffcf 100644
--- a/rails-pg-adapter.gemspec
+++ b/rails-pg-adapter.gemspec
@@ -28,7 +28,7 @@ Gem::Specification.new do |spec|
   end
   spec.require_paths = ["lib"]
 
-  spec.add_dependency("rails", "~> 6")
+  spec.add_dependency("rails", "~> 6", "<7")
 
   spec.metadata = { "rubygems_mfa_required" => "true" } if spec.respond_to?(:metadata=)
 end