--- a/mercurial/hgweb/webcommands.py	Sun Apr 01 23:34:29 2018 +0900
+++ b/mercurial/hgweb/webcommands.py	Sun Apr 01 23:40:08 2018 +0900
@@ -1084,7 +1084,7 @@
         linerange = webutil.formatlinerange(*lrange)
         # deactivate numeric nav links when linerange is specified as this
         # would required a dedicated "revnav" class
-        nav = []
+        nav = templateutil.mappinglist([])
         if descend:
             it = dagop.blockdescendants(fctx, *lrange)
         else: