diff --git a/mercurial/templater.py b/mercurial/templater.py
--- a/mercurial/templater.py
+++ b/mercurial/templater.py
@@ -397,7 +397,7 @@
         # pair instead of **props
         props = context._resources.copy()
         props.update(mapping)
-        return v(**props)
+        return v(**pycompat.strkwargs(props))
     return v
 
 def buildtemplate(exp, context):