diff --git a/display.py b/display.py
index 25cb0a2..99cf33e 100644
--- a/display.py
+++ b/display.py
@@ -259,7 +259,7 @@ class DisplayHTMLPage(object):
         self.blocks.append(block)
 
     def build(self, root):
-        filename = root + self.filename
+        filename = os.path.join(root, self.filename)
 
         base = os.path.dirname(filename)
         if not os.path.exists(base):