diff --git a/tool/rbinstall.rb b/tool/rbinstall.rb
index f28a183356..7cb584bdd7 100755
--- a/tool/rbinstall.rb
+++ b/tool/rbinstall.rb
@@ -827,7 +827,7 @@ module RbInstall
         end
 
         def ext_features
-          loaded_gemspec = Gem::Specification.load("#{root}/#{gemspec}")
+          loaded_gemspec = load_gemspec("#{root}/#{gemspec}")
           extension = loaded_gemspec.extensions.first
           return [] unless extension