Index: TODO
===================================================================
diff -u -red0f5cba982af963b62c36d8c8c75e89c81adf3e -r4b78042d08af7f3200d51f4033d5164c949f332d
--- TODO	(.../TODO)	(revision ed0f5cba982af963b62c36d8c8c75e89c81adf3e)
+++ TODO	(.../TODO)	(revision 4b78042d08af7f3200d51f4033d5164c949f332d)
@@ -5843,21 +5843,21 @@
 
 - Added Rosetta example: https://rosettacode.org/wiki/Add_a_variable_to_a_class_instance_at_runtime
 
-========================================================================
-TODO:
-
 - Improve error message with {*} operator, not 'unknown'.
 
 Object new {
     :object method foo {a b c args} { puts --[current method]}
-    {*}[list :foo 1 2 3 4 5 6]; # Should be equivalendt to ':foo 1 2 3 4 5 6', but isn't
-    : {*}[list foo 1 2 3 4 5 6]; # Should be equivalent to ':foo 1 2 3 4 5 6', but isn't
+    {*}[list :foo 1 2 3 4 5 6]; 
+    : {*}[list foo 1 2 3 4 5 6];
     catch {:{*}[list foo 1 2 3 4 5 6]} msg; puts msg=$msg
 }
 
 proc =foo {a b c args} { puts foo }
 catch {={*}[list foo 1 2 3 4 5 6]} msg; puts msg=$msg
 
+========================================================================
+TODO:
+
 - Under core-8-5-branch, make test --enable-development yields an assertion failure:
 
   ./tests/parameters.test
Index: generic/nsf.c
===================================================================
diff -u -re20e1c1aa5e3b8f1020a455605d6f971ab622f5b -r4b78042d08af7f3200d51f4033d5164c949f332d
--- generic/nsf.c	(.../nsf.c)	(revision e20e1c1aa5e3b8f1020a455605d6f971ab622f5b)
+++ generic/nsf.c	(.../nsf.c)	(revision 4b78042d08af7f3200d51f4033d5164c949f332d)
@@ -14207,23 +14207,24 @@
 
   } else { /* no unknown called, this is the built-in unknown handler */
     Tcl_Obj *tailMethodObj = NULL;
-
     if (objc > 1 && ((*methodName) == '-' || (unknownObj && objv[0] == unknownObj))) {
       int length;
-      if (Tcl_ListObjLength(interp, objv[1], &length) == TCL_OK && length > 0) {
-        Tcl_ListObjIndex(interp, objv[1], length - 1, &tailMethodObj);
+      tailMethodObj = objv[1];
+      if (Tcl_ListObjLength(interp, objv[1], &length) == TCL_OK) {
+        if (length > 1) {
+          Tcl_ListObjIndex(interp, objv[1], length - 1, &tailMethodObj);
+        } 
       }
     }
-
     result = NsfPrintError(interp, "%s: unable to dispatch method '%s'",
                            ObjectName_(object), (tailMethodObj != NULL) ? MethodName(tailMethodObj) : methodName);
   }
-
+  
   /*
    * Reset interp state, unknown has been fired.
    */
   rst->unknown = 0;
-
+  
   return result;
 }
 
Index: tests/methods.test
===================================================================
diff -u -r3c1482d9e1f80f0216250f5debade5d8edb1b17e -r4b78042d08af7f3200d51f4033d5164c949f332d
--- tests/methods.test	(.../methods.test)	(revision 3c1482d9e1f80f0216250f5debade5d8edb1b17e)
+++ tests/methods.test	(.../methods.test)	(revision 4b78042d08af7f3200d51f4033d5164c949f332d)
@@ -230,6 +230,60 @@
   ? {o eval :foo} "::o: unable to dispatch method 'foo'" 
 }
 
+nx::test case colon-unknown {
+  set o [nx::Object new {
+    :object method foo {a b c args} { return [current method]-ok }
+
+    ## Expansion to valid method calls (messages)
+    :object method expand-non-empty-list-1 {} {
+      {*}[list :foo 1 2 3 4 5 6];
+    }
+    :object method expand-non-empty-list-2 {} {
+      : {*}[list foo 1 2 3 4 5 6];
+    }
+    :object method expand-self-call-1 {} {
+      {*}[list :];
+    }
+    :object method expand-self-call-2 {} {
+      : {*}[list];
+    }
+
+    ## (Non-)expansion & unknown
+    :object method expand-unknown-1 {} {
+      :{*}[list foo 1 2 3 4 5 6]; # no expansion, yielding invalid list as method name
+    }
+    :object method expand-unknown-2 {} {
+      :{*}[list]; # no expansion, yielding invalid list as method name
+    }
+    :object method expand-unknown-3 {} {
+      :{*}; # no expansion, yielding invalid list as method name
+    }
+    :object method expand-unknown-4 {} {
+      :{*}{}; # no expansion, yielding invalid list as method name
+    }
+    :object method expand-unknown-5 {} {
+      :{\}}; # yet another invalid list (no expansion op)
+    }
+  }]
+
+  ? [list $o expand-non-empty-list-1] "foo-ok"
+  ? [list $o expand-non-empty-list-2] "foo-ok"
+  ? [list $o expand-self-call-1] $o
+  ? [list $o expand-self-call-2] $o
+
+  #
+  # Keep unknown messages compatible with Tcl's 'invalid command'
+  # messages in the cases below, e.g.: 
+  #
+  # proc =foo {args} {;}; ={*}[list foo 1 2 3 4 5 6]
+  #
+  ? [list $o expand-unknown-1] "$o: unable to dispatch method '{*}foo 1 2 3 4 5 6'"
+  ? [list $o expand-unknown-2] "$o: unable to dispatch method '{*}'"
+  ? [list $o expand-unknown-3] "$o: unable to dispatch method '{*}'"
+  ? [list $o expand-unknown-4] "$o: unable to dispatch method '{*}{}'"
+  ? [list $o expand-unknown-5] "$o: unable to dispatch method '{\}}'"
+}
+
 nx::test case mixinguards {
   # define a Class C and mixin class M
   nx::Class create C