diff --git a/python/lsst/pex/config/configDictField.py b/python/lsst/pex/config/configDictField.py
index ef675b1..fd187af 100644
--- a/python/lsst/pex/config/configDictField.py
+++ b/python/lsst/pex/config/configDictField.py
@@ -59,7 +59,7 @@ def __setitem__(self, k, x, at=None, label="setitem", setHistory=True):
 
         # validate itemtype
         dtype = self._field.itemtype
-        if type(x) != self._field.itemtype and x != self._field.itemtype:
+        if not isinstance(x, self._field.itemtype) and x != self._field.itemtype:
             msg = "Value {} at key {!r} is of incorrect type {}. Expected type {}".format(
                 x,
                 k,
@@ -76,7 +76,7 @@ def __setitem__(self, k, x, at=None, label="setitem", setHistory=True):
             if x == dtype:
                 self._dict[k] = dtype(__name=name, __at=at, __label=label)
             else:
-                self._dict[k] = dtype(__name=name, __at=at, __label=label, **x._storage)
+                self._dict[k] = x.__class__(__name=name, __at=at, __label=label, **x._storage)
             if setHistory:
                 self.history.append(("Added item at key %s" % k, at, label))
         else: