diff --git a/src/libboard_artiq/src/si549.rs b/src/libboard_artiq/src/si549.rs
index 8d7091b..5ced94c 100644
--- a/src/libboard_artiq/src/si549.rs
+++ b/src/libboard_artiq/src/si549.rs
@@ -795,7 +795,7 @@ pub mod wrpll_refclk {
 
             let locked = unsafe { csr::wrpll_refclk::mmcm_locked_read() == 1 };
             if !locked {
-                return Err("mmcm failed to generate 125Mhz ref clock from SMA CLKIN");
+                return Err("mmcm failed to generate 125MHz ref clock from SMA CLKIN");
             }
         }