Index: Python/ast.c
===================================================================
--- Python/ast.c	(Revision 47289)
+++ Python/ast.c	(Arbeitskopie)
@@ -2142,6 +2142,10 @@
  loop:
     switch (TYPE(n)) {
         case import_as_name:
+            if (NCH(n) == 3 && strcmp(STR(CHILD(n, 1)), "as") != 0) {
+                ast_error(n, "invalid syntax");
+                return NULL;
+            }
             str = (NCH(n) == 3) ? NEW_IDENTIFIER(CHILD(n, 2)) : NULL;
             return alias(NEW_IDENTIFIER(CHILD(n, 0)), str, c->c_arena);
         case dotted_as_name:
@@ -2150,6 +2154,10 @@
                 goto loop;
             }
             else {
+                if (strcmp(STR(CHILD(n, 1)), "as") != 0) {
+                    ast_error(n, "invalid syntax");
+                    return NULL;
+                }
                 alias_ty a = alias_for_import_name(c, CHILD(n, 0));
                 assert(!a->asname);
                 a->asname = NEW_IDENTIFIER(CHILD(n, 2));