diff --git a/src/mock_vws/_query_validators/__init__.py b/src/mock_vws/_query_validators/__init__.py
index 5258bb3c1..424db3743 100644
--- a/src/mock_vws/_query_validators/__init__.py
+++ b/src/mock_vws/_query_validators/__init__.py
@@ -208,7 +208,7 @@ def validate_content_type_header(
 
     if 'boundary' not in pdict:
         context.status_code = codes.BAD_REQUEST
-        context.headers['Content-Type'] = 'text/html'
+        context.headers['Content-Type'] = 'text/html;charset=UTF-8'
         return (
             'java.io.IOException: RESTEASY007550: '
             'Unable to get boundary for multipart'
diff --git a/tests/mock_vws/test_query.py b/tests/mock_vws/test_query.py
index 5e3f68050..e86c4374c 100644
--- a/tests/mock_vws/test_query.py
+++ b/tests/mock_vws/test_query.py
@@ -219,7 +219,7 @@ def test_no_boundary(
         assert_vwq_failure(
             response=response,
             status_code=codes.BAD_REQUEST,
-            content_type='text/html',
+            content_type='text/html;charset=UTF-8',
         )
 
     def test_bogus_boundary(