diff --git a/artiq/firmware/ksupport/api.rs b/artiq/firmware/ksupport/api.rs
index 60e11b80a..1cf3ce884 100644
--- a/artiq/firmware/ksupport/api.rs
+++ b/artiq/firmware/ksupport/api.rs
@@ -71,6 +71,7 @@ static mut API: &'static [(&'static str, *const ())] = &[
     /* libm */
     api!(sqrt),
     api!(round),
+    api!(floor),
 
     /* exceptions */
     api!(_Unwind_Resume = ::unwind::_Unwind_Resume),