diff --git a/contrib/codegen/src/lib.rs b/contrib/codegen/src/lib.rs
index 512267b9..57b85bcd 100644
--- a/contrib/codegen/src/lib.rs
+++ b/contrib/codegen/src/lib.rs
@@ -26,6 +26,7 @@
 //! DATABASE_NAME := (string literal)
 //! </pre>
 
+#[allow(unused_extern_crates)]
 extern crate proc_macro;
 
 #[allow(unused_imports)]
diff --git a/core/codegen/src/lib.rs b/core/codegen/src/lib.rs
index e2cb6e99..07132a21 100644
--- a/core/codegen/src/lib.rs
+++ b/core/codegen/src/lib.rs
@@ -59,7 +59,7 @@
 //! ```
 
 #[macro_use] extern crate quote;
-extern crate proc_macro;
+#[allow(unused_extern_crates)] extern crate proc_macro;
 
 use rocket_http as http;