diff --git a/src/pip/_internal/index/collector.py b/src/pip/_internal/index/collector.py
index 321861e2c..7908ab996 100644
--- a/src/pip/_internal/index/collector.py
+++ b/src/pip/_internal/index/collector.py
@@ -457,7 +457,7 @@ def _get_html_page(link, session=None):
     except _NotHTML as exc:
         logger.warning(
             'Skipping page %s because the %s request got Content-Type: %s.'
-            'The supported Content-Type is text/html',
+            'The only supported Content-Type is text/html',
             link, exc.request_desc, exc.content_type,
         )
     except HTTPError as exc:
diff --git a/tests/unit/test_collector.py b/tests/unit/test_collector.py
index 9a7966688..0387813ad 100644
--- a/tests/unit/test_collector.py
+++ b/tests/unit/test_collector.py
@@ -501,7 +501,7 @@ def test_get_html_page_invalid_content_type(caplog, content_type):
     assert ('pip._internal.index.collector',
             logging.WARNING,
             'Skipping page {} because the GET request got Content-Type: {}.'
-            'The supported Content-Type is text/html'.format(
+            'The only supported Content-Type is text/html'.format(
                 url, content_type)) \
         in caplog.record_tuples