Index: generic/tclEncoding.c
==================================================================
--- generic/tclEncoding.c
+++ generic/tclEncoding.c
@@ -353,10 +353,11 @@
 DupEncodingIntRep(
     Tcl_Obj *srcPtr,
     Tcl_Obj *dupPtr)
 {
     dupPtr->internalRep.twoPtrValue.ptr1 = Tcl_GetEncoding(NULL, srcPtr->bytes);
+    dupPtr->typePtr = &encodingType;
 }
 
 /*
  *----------------------------------------------------------------------
  *