Index: generic/nsf.c
===================================================================
diff -u -N -r74b7a4066526ff5f5a8080ed907f71c9ed5c7700 -r657e7e3b20ca1ad11c75634ecb04aeebb8edef97
--- generic/nsf.c	(.../nsf.c)	(revision 74b7a4066526ff5f5a8080ed907f71c9ed5c7700)
+++ generic/nsf.c	(.../nsf.c)	(revision 657e7e3b20ca1ad11c75634ecb04aeebb8edef97)
@@ -22342,10 +22342,16 @@
    * creating objects of this class.
    */
 
-  if (likely(class && class->parsedParamPtr)) {
+  if (likely(class && class->parsedParamPtr) 
+#if defined(PER_OBJECT_PARAMETER_CACHING)
+      && class->classParamPtrEpoch == RUNTIME_STATE(interp)->classParamPtrEpoch
+#endif
+      ) {
     NsfParsedParam *clParsedParamPtr = class->parsedParamPtr;
     parsedParamPtr->paramDefs = clParsedParamPtr->paramDefs;
     parsedParamPtr->possibleUnknowns = clParsedParamPtr->possibleUnknowns;
+    /* fprintf(stderr, "reuse class param for class %p  %s paramPtr %p\n",
+       class, ClassName(class), clParsedParamPtr);*/
     result = TCL_OK;
 
 #if defined(PER_OBJECT_PARAMETER_CACHING)
@@ -22391,8 +22397,14 @@
 	  ppDefPtr->paramDefs = parsedParamPtr->paramDefs;
 	  ppDefPtr->possibleUnknowns = parsedParamPtr->possibleUnknowns;
 	  if (class) {
-	    class->parsedParamPtr = ppDefPtr;
 #if defined(PER_OBJECT_PARAMETER_CACHING)
+            if (class->parsedParamPtr) {
+              NsfParameterInvalidateClassCacheCmd(interp, class);
+            }
+	    class->classParamPtrEpoch = RUNTIME_STATE(interp)->classParamPtrEpoch;
+#endif
+            class->parsedParamPtr = ppDefPtr;
+#if defined(PER_OBJECT_PARAMETER_CACHING)
 	  } else {
 	    NsfObjectOpt *opt = NsfRequireObjectOpt(object);
 	    if (object->opt->parsedParamPtr) {
Index: generic/nsfInt.h
===================================================================
diff -u -N -r7401c1c91b67a9adc5b3c1a9049a37a9d8e13c93 -r657e7e3b20ca1ad11c75634ecb04aeebb8edef97
--- generic/nsfInt.h	(.../nsfInt.h)	(revision 7401c1c91b67a9adc5b3c1a9049a37a9d8e13c93)
+++ generic/nsfInt.h	(.../nsfInt.h)	(revision 657e7e3b20ca1ad11c75634ecb04aeebb8edef97)
@@ -535,6 +535,9 @@
   Tcl_HashTable instances;
   Tcl_Namespace *nsPtr;
   NsfParsedParam *parsedParamPtr;
+#if defined(PER_OBJECT_PARAMETER_CACHING)
+  int classParamPtrEpoch;
+#endif
   NsfClassOpt *opt;
   short color;
 } NsfClass;