Index: django/contrib/admin/options.py
===================================================================
--- django/contrib/admin/options.py     (revision 5751)
+++ django/contrib/admin/options.py     (working copy)
@@ -88,9 +88,9 @@
         classes = []
         if self.is_checkbox:
             classes.append(u'vCheckboxLabel')
-            contents = escape(self.field.label)
+            contents = escape(force_unicode(self.field.label))
         else:
-            contents = escape(self.field.label) + u':'
+            contents = escape(force_unicode(self.field.label)) + u':'
         if self.field.field.required:
             classes.append(u'required')
         if not self.is_first: