diff --git a/Gemfile.lock b/Gemfile.lock
index 70bce5b..72c4962 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -28,7 +28,7 @@ GEM
       simplecov_json_formatter (~> 0.1)
     simplecov-html (0.12.3)
     simplecov_json_formatter (0.1.4)
-    stringio (3.0.1)
+    stringio (3.1.0)
     test-unit (3.5.3)
       power_assert
     vcr (3.0.3)