diff --git a/sinatra-contrib/sinatra-contrib.gemspec b/sinatra-contrib/sinatra-contrib.gemspec
index 3a05e39558..7149d5947b 100644
--- a/sinatra-contrib/sinatra-contrib.gemspec
+++ b/sinatra-contrib/sinatra-contrib.gemspec
@@ -46,7 +46,7 @@ RubyGems 2.0 or newer is required to protect against public gem pushes. You can
   s.add_development_dependency 'asciidoctor'
   s.add_development_dependency 'builder'
   s.add_development_dependency 'erubi'
-  s.add_development_dependency 'haml'
+  s.add_development_dependency 'haml', '~> 5'
   s.add_development_dependency 'liquid'
   s.add_development_dependency 'markaby'
   s.add_development_dependency 'nokogiri'