diff --git a/wolframalpha/__init__.py b/wolframalpha/__init__.py
index bfe9ad1..d1b28a9 100644
--- a/wolframalpha/__init__.py
+++ b/wolframalpha/__init__.py
@@ -126,7 +126,7 @@ async def aquery(self, input, params=(), **kwargs):
                     params, appid=self.app_id, input=input, **kwargs
                 ),
             )
-        assert resp.headers['Content-Type'] == 'text/xml;charset=utf-8'
+        assert resp.headers['Content-Type'] == 'text/xml; charset=utf-8'
         doc = xmltodict.parse(resp.content, postprocessor=Document.make)
         return doc['queryresult']