diff --git a/html5lib/filters/sanitizer.py b/html5lib/filters/sanitizer.py
index e852f53b..ce67b7de 100644
--- a/html5lib/filters/sanitizer.py
+++ b/html5lib/filters/sanitizer.py
@@ -825,7 +825,7 @@ def allowed_token(self, token):
                 if uri and uri.scheme:
                     if uri.scheme not in self.allowed_protocols:
                         del attrs[attr]
-                    if uri.scheme == 'data':
+                    elif uri.scheme == 'data':
                         m = data_content_type.match(uri.path)
                         if not m:
                             del attrs[attr]