Index: generic/nsf.c
===================================================================
diff -u -N -rbc7f267ac8f8439d87c710917eabcd6f65f22816 -r71dcbd9cdd5b6d564c0c1c831825e2579f1abb46
--- generic/nsf.c	(.../nsf.c)	(revision bc7f267ac8f8439d87c710917eabcd6f65f22816)
+++ generic/nsf.c	(.../nsf.c)	(revision 71dcbd9cdd5b6d564c0c1c831825e2579f1abb46)
@@ -16442,7 +16442,10 @@
   nonnull_assert(defObject != NULL);
 
   methodName = ObjStr(nameObj);
-  assert(*methodName != ':');
+  /*
+   * Tcl (at least in newer versions) will raise an error in cases, where
+   * the methodName starts with a colon.
+   */
 
   if (regObject == NULL) {
     regObject = defObject;
@@ -25906,6 +25909,7 @@
 
   if (cl == NULL) {
     RequireObjNamespace(interp, defObject);
+
   }
   return MakeMethod(interp, defObject, regObject, cl,
                     nameObj, arguments, body,