Index: compilers/imcc/symreg.c
===================================================================
--- compilers/imcc/symreg.c	(revision 39633)
+++ compilers/imcc/symreg.c	(working copy)
@@ -600,10 +600,16 @@
 {
     ASSERT_ARGS(mk_ident)
     char   * const fullname = _mk_fullname(pesky_global__namespace, name);
-    SymReg        *r        = mk_symreg(interp, fullname, t);
+    SymReg *r = _get_sym_typed(&(IMCC_INFO(interp)->last_unit->hash), name, t);
+    if (r)
+        IMCC_fataly(interp, EXCEPTION_SYNTAX_ERROR,
+                "syntax error, duplicated IDENTIFIER '%s'", fullname);
 
+    r = mk_symreg(interp, fullname, t);
+
     r->type = VTIDENTIFIER;
 
+
     if (pesky_global__namespace) {
         Identifier * const ident = mem_allocate_zeroed_typed(Identifier);