Index: generic/nsf.c
===================================================================
diff -u -rce0ccaa71d0383f20978031448b1fb3adabec3ad -r277704be44e8205d6aa0507c840e44223039f841
--- generic/nsf.c	(.../nsf.c)	(revision ce0ccaa71d0383f20978031448b1fb3adabec3ad)
+++ generic/nsf.c	(.../nsf.c)	(revision 277704be44e8205d6aa0507c840e44223039f841)
@@ -14432,9 +14432,9 @@
   size_t j, length;
   int result;
 
-  if (*methodName == '-') {
+  if (*methodName == '-' || *methodName == ':') {
     return NsfVarErrMsg(interp,
-                          "method name \"", methodName, "\" must not start with a dash",
+                          "invalid setter name \"", methodName, "\" (must not start with a dash or colon)",
                           (char *) NULL);
 
   }