diff --git a/src/calibre/gui2/viewer/documentview.py b/src/calibre/gui2/viewer/documentview.py
index 6566faecbc..415211162e 100644
--- a/src/calibre/gui2/viewer/documentview.py
+++ b/src/calibre/gui2/viewer/documentview.py
@@ -921,6 +921,9 @@ class DocumentView(QWebView):  # {{{
     def load_path(self, path, pos=0.0):
         self.initial_pos = pos
         self.last_loaded_path = path
+        # This is needed otherwise percentage margins on body are not correctly
+        # evaluated in read_document_margins() in paged mode.
+        self.document.setPreferredContentsSize(QSize())
 
         def callback(lu):
             self.loading_url = lu