Index: Python/ast.c
===================================================================
--- Python/ast.c	(Revision 45742)
+++ Python/ast.c	(Arbeitskopie)
@@ -1702,7 +1702,7 @@
       argument: [test '='] test [gen_for]	 # Really [keyword '='] test
     */
 
-    int i, nargs, nkeywords, ngens;
+    int i, nargs, nkeywords, ngens, seen_kw = 0;
     asdl_seq *args;
     asdl_seq *keywords;
     expr_ty vararg = NULL, kwarg = NULL;
@@ -1747,6 +1747,10 @@
 	if (TYPE(ch) == argument) {
 	    expr_ty e;
 	    if (NCH(ch) == 1) {
+		if (seen_kw) {
+		    ast_error(CHILD(ch, 0), "non-keyword arg after keyword arg");
+		    return NULL;
+		}
 		e = ast_for_expr(c, CHILD(ch, 0));
                 if (!e)
                     return NULL;
@@ -1786,6 +1790,7 @@
                 if (!kw)
                     return NULL;
 		asdl_seq_SET(keywords, nkeywords++, kw);
+		seen_kw = 1;
 	    }
 	}
 	else if (TYPE(ch) == STAR) {
Index: Lib/test/test_syntax.py
===================================================================
--- Lib/test/test_syntax.py	(Revision 45742)
+++ Lib/test/test_syntax.py	(Arbeitskopie)
@@ -290,6 +290,9 @@
             :""")
         self._check_error(source, "nested scope")
 
+    def test_kwargs_last(self):
+        self._check_error("int(base=10, '2')", "non-keyword arg")
+
 def test_main():
     test_support.run_unittest(SyntaxTestCase)
     from test import test_syntax