diff --git a/pytest_html/plugin.py b/pytest_html/plugin.py
index 5b2de9d8..02b14378 100644
--- a/pytest_html/plugin.py
+++ b/pytest_html/plugin.py
@@ -161,13 +161,13 @@ def append_extra_html(self, extra, extra_index, test_index):
             if extra.get('format') == extras.FORMAT_IMAGE:
                 content = extra.get('content')
                 try:
-                    is_file = (content.startswith(('file', 'http')) or
-                               isfile(content))
+                    is_uri_or_path = (content.startswith(('file', 'http')) or
+                                      isfile(content))
                 except ValueError:
                     # On Windows, os.path.isfile throws this exception when
                     # passed a b64 encoded image.
-                    is_file = False
-                if is_file:
+                    is_uri_or_path = False
+                if is_uri_or_path:
                     if self.self_contained:
                         warnings.warn('Self-contained HTML report '
                                       'includes link to external '