diff --git a/Gemfile b/Gemfile
index 11be29977..67b8b9a13 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,3 +22,6 @@ if RUBY_VERSION >= "3.0.0"
   gem "rbs"
   gem "prism", ">= 0.18.0"
 end
+
+# Remove this after stringio 3.1.0 is released
+gem "stringio", github: "ruby/stringio"