diff --git a/artiq/firmware/libboard/hmc830_7043.rs b/artiq/firmware/libboard/hmc830_7043.rs
index 41e8e4f18..dfbd28b84 100644
--- a/artiq/firmware/libboard/hmc830_7043.rs
+++ b/artiq/firmware/libboard/hmc830_7043.rs
@@ -10,9 +10,9 @@
  * sysref clock: 15.625MHz (div=64)
  */
 
-use clock;
 
 mod hmc830 {
+    use clock;
     use csr;
 
     const HMC830_WRITES: [(u8, u32); 16] = [