diff --git a/Python/ast.c b/Python/ast.c
index 79c9403..6ec2ef1 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -1968,7 +1968,8 @@
             }
             else {
                 keyword_ty kw;
-                identifier key;
+                identifier key, tmp;
+                int k;
 
                 /* CHILD(ch, 0) is test, but must be an identifier? */ 
                 e = ast_for_expr(c, CHILD(ch, 0));
@@ -1989,6 +1990,13 @@
 		  return NULL;
 		}
                 key = e->v.Name.id;
+                for (k = 0; k < nkeywords; k++) {
+                    tmp = ((keyword_ty)asdl_seq_GET(keywords, k))->arg;
+                    if (!PyUnicode_Compare(tmp, key)) {
+                        ast_error(CHILD(ch, 0), "keyword argument repeated");
+                        return NULL;
+                    }
+                }
                 e = ast_for_expr(c, CHILD(ch, 2));
                 if (!e)
                     return NULL;