diff --git a/mercurial/templatefilters.py b/mercurial/templatefilters.py
--- a/mercurial/templatefilters.py
+++ b/mercurial/templatefilters.py
@@ -18,6 +18,7 @@ from . import (
     node,
     pycompat,
     registrar,
+    smartset,
     templateutil,
     url,
     util,
@@ -108,6 +109,9 @@ def basename(path):
 @templatefilter(b'cbor')
 def cbor(obj):
     """Any object. Serializes the object to CBOR bytes."""
+    if isinstance(obj, smartset.abstractsmartset):
+        # cborutil is stricter about type than json() filter
+        obj = list(obj)
     return b''.join(cborutil.streamencode(obj))
 
 
diff --git a/mercurial/templateutil.py b/mercurial/templateutil.py
--- a/mercurial/templateutil.py
+++ b/mercurial/templateutil.py
@@ -474,7 +474,7 @@ class revslist(wrapped):
         return bool(self._revs)
 
     def tovalue(self, context, mapping):
-        return list(self._revs)
+        return self._revs
 
 
 class _mappingsequence(wrapped):