diff --git a/spec/basic/48_case_conversion/expected_output.css b/spec/basic/48_case_conversion/expected_output.css
index 7fc8ea399f..4521c08303 100644
--- a/spec/basic/48_case_conversion/expected_output.css
+++ b/spec/basic/48_case_conversion/expected_output.css
@@ -1,3 +1,4 @@
+@charset "UTF-8";
 div {
   bar: "BLAH";
   bar: "BLAH";