diff --git a/artiq/runtime.rs/libksupport/api.rs b/artiq/runtime.rs/libksupport/api.rs
index 5a12ea691..dbfbd759b 100644
--- a/artiq/runtime.rs/libksupport/api.rs
+++ b/artiq/runtime.rs/libksupport/api.rs
@@ -105,9 +105,14 @@ static mut API: &'static [(&'static str, *const ())] = &[
     api!(rtio_input_timestamp = ::rtio::input_timestamp),
     api!(rtio_input_data = ::rtio::input_data),
 
+    #[cfg(has_i2c)]
     api!(i2c_init = ::i2c::init),
+    #[cfg(has_i2c)]
     api!(i2c_start = ::i2c::start),
+    #[cfg(has_i2c)]
     api!(i2c_stop = ::i2c::stop),
+    #[cfg(has_i2c)]
     api!(i2c_write = ::i2c::write),
+    #[cfg(has_i2c)]
     api!(i2c_read = ::i2c::read),
 ];
diff --git a/artiq/runtime.rs/libksupport/lib.rs b/artiq/runtime.rs/libksupport/lib.rs
index 6b285f889..027c0e3b3 100644
--- a/artiq/runtime.rs/libksupport/lib.rs
+++ b/artiq/runtime.rs/libksupport/lib.rs
@@ -50,6 +50,7 @@ macro_rules! artiq_raise {
 }
 
 mod rtio;
+#[cfg(has_i2c)]
 mod i2c;
 
 use core::{mem, ptr, slice, str};