diff --git a/lib/rdoc/rdoc.gemspec b/lib/rdoc/rdoc.gemspec
index fd222d47e0..6146e09bb6 100644
--- a/lib/rdoc/rdoc.gemspec
+++ b/lib/rdoc/rdoc.gemspec
@@ -243,4 +243,6 @@ RDoc includes the +rdoc+ and +ri+ tools for generating and displaying documentat
 
   s.required_ruby_version = Gem::Requirement.new(">= 2.4.0")
   s.required_rubygems_version = Gem::Requirement.new(">= 2.2")
+
+  s.add_development_dependency("gettext")
 end