diff --git a/tests/test_api.py b/tests/test_api.py
index 16def4b69..cc65249f5 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -52,7 +52,9 @@ def _test_resource(class_, basename, check, **kwargs):
     check(class_(relative_path, **kwargs))
     kwargs.pop('base_url', None)
     check(class_(string=content, base_url=relative_filename, **kwargs))
-    encoding = kwargs.get('encoding') or 'utf-8'
+    encoding = kwargs.pop('encoding', 'utf-8')
+    with open(absolute_filename, 'r', encoding=encoding) as fd:
+        check(class_(file_obj=fd, **kwargs))
     check(class_(string=content.decode(encoding),  # unicode
                  base_url=relative_filename, **kwargs))
     with pytest.raises(TypeError):
diff --git a/weasyprint/__init__.py b/weasyprint/__init__.py
index 47aa905fb..52094a372 100644
--- a/weasyprint/__init__.py
+++ b/weasyprint/__init__.py
@@ -162,10 +162,12 @@ def __init__(self, guess=None, filename=None, url=None, file_obj=None,
             if isinstance(source, str):
                 result = html5lib.parse(source, namespaceHTMLElements=False)
             else:
-                result = html5lib.parse(
-                    source, override_encoding=encoding,
-                    transport_encoding=protocol_encoding,
-                    namespaceHTMLElements=False)
+                kwargs = {'namespaceHTMLElements': False}
+                if protocol_encoding is not None:
+                    kwargs['transport_encoding'] = protocol_encoding
+                if encoding is not None:
+                    kwargs['override_encoding'] = encoding
+                result = html5lib.parse(source, **kwargs)
         self.base_url = _find_base_url(result, base_url)
         self.url_fetcher = url_fetcher
         self.media_type = media_type
@@ -281,12 +283,12 @@ def __init__(self, guess=None, filename=None, url=None, file_obj=None,
             base_url=base_url, url_fetcher=url_fetcher,
             check_css_mime_type=_check_mime_type)
         with result as (source_type, source, base_url, protocol_encoding):
-            if source_type == 'string' and not isinstance(source, bytes):
+            if source_type == 'file_obj':
+                source = source.read()
+            if isinstance(source, str):
                 # unicode, no encoding
                 stylesheet = tinycss2.parse_stylesheet(source)
             else:
-                if source_type == 'file_obj':
-                    source = source.read()
                 stylesheet, encoding = tinycss2.parse_stylesheet_bytes(
                     source, environment_encoding=encoding,
                     protocol_encoding=protocol_encoding)