diff --git a/serde/build.rs b/serde/build.rs
index 261ed52ab..c32872b95 100644
--- a/serde/build.rs
+++ b/serde/build.rs
@@ -17,6 +17,7 @@ fn main() {
         println!("cargo:rustc-check-cfg=cfg(no_core_cstr)");
         println!("cargo:rustc-check-cfg=cfg(no_core_num_saturating)");
         println!("cargo:rustc-check-cfg=cfg(no_core_try_from)");
+        println!("cargo:rustc-check-cfg=cfg(no_diagnostic_namespace)");
         println!("cargo:rustc-check-cfg=cfg(no_float_copysign)");
         println!("cargo:rustc-check-cfg=cfg(no_num_nonzero_signed)");
         println!("cargo:rustc-check-cfg=cfg(no_relaxed_trait_bounds)");
@@ -25,7 +26,6 @@ fn main() {
         println!("cargo:rustc-check-cfg=cfg(no_std_atomic64)");
         println!("cargo:rustc-check-cfg=cfg(no_systemtime_checked_add)");
         println!("cargo:rustc-check-cfg=cfg(no_target_has_atomic)");
-        println!("cargo:rustc-check-cfg=cfg(no_diagnostic_namespace)");
     }
 
     let target = env::var("TARGET").unwrap();