diff --git a/nmigen/back/verilog.py b/nmigen/back/verilog.py
index 3c7be2b..19a91e4 100644
--- a/nmigen/back/verilog.py
+++ b/nmigen/back/verilog.py
@@ -1,8 +1,3 @@
-import os
-import re
-import subprocess
-import itertools
-
 from .._yosys import *
 from . import rtlil