diff --git a/serde_codegen/src/lib.rs b/serde_codegen/src/lib.rs
index c2f7d1f2..ba18584b 100644
--- a/serde_codegen/src/lib.rs
+++ b/serde_codegen/src/lib.rs
@@ -182,12 +182,16 @@ mod shim {
 }
 
 #[cfg(feature = "with-syn")]
+#[doc(hidden)]
+/// Not public API. Use the serde_derive crate.
 pub fn expand_derive_serialize(item: &str) -> Result<String, String> {
     let syn_item = syn::parse_macro_input(item).unwrap();
     ser::expand_derive_serialize(&syn_item).map(|derive| derive.to_string())
 }
 
 #[cfg(feature = "with-syn")]
+#[doc(hidden)]
+/// Not public API. Use the serde_derive crate.
 pub fn expand_derive_deserialize(item: &str) -> Result<String, String> {
     let syn_item = syn::parse_macro_input(item).unwrap();
     de::expand_derive_deserialize(&syn_item).map(|derive| derive.to_string())