diff --git a/serde/build.rs b/serde/build.rs
index 3a25498dae..f0aec2fbc1 100644
--- a/serde/build.rs
+++ b/serde/build.rs
@@ -13,6 +13,20 @@ fn main() {
         None => return,
     };
 
+    if minor >= 77 {
+        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_float_copysign)");
+        println!("cargo:rustc-check-cfg=cfg(no_num_nonzero_signed)");
+        println!("cargo:rustc-check-cfg=cfg(no_relaxed_trait_bounds)");
+        println!("cargo:rustc-check-cfg=cfg(no_serde_derive)");
+        println!("cargo:rustc-check-cfg=cfg(no_std_atomic)");
+        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)");
+    }
+
     // TryFrom was stabilized in Rust 1.34:
     // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#tryfrom-and-tryinto
     if minor < 34 {
diff --git a/serde_derive_internals/Cargo.toml b/serde_derive_internals/Cargo.toml
index 095a7439cd..bf99c13998 100644
--- a/serde_derive_internals/Cargo.toml
+++ b/serde_derive_internals/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive_internals"
-version = "0.29.0"
+version = "0.29.1"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 description = "AST representation used by Serde derive macros. Unstable."
 documentation = "https://docs.rs/serde_derive_internals"
diff --git a/serde_derive_internals/build.rs b/serde_derive_internals/build.rs
index 25b5ef3132..b2bbb3a561 100644
--- a/serde_derive_internals/build.rs
+++ b/serde_derive_internals/build.rs
@@ -1,9 +1,17 @@
 use std::path::Path;
 
 fn main() {
+    // Warning: build.rs is not published to crates.io.
+
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=src/mod.rs");
 
+    println!("cargo:rustc-cfg=check_cfg");
+    println!("cargo:rustc-check-cfg=cfg(check_cfg)");
+    println!("cargo:rustc-check-cfg=cfg(exhaustive)");
+    println!("cargo:rustc-check-cfg=cfg(serde_build_from_git)");
+    println!("cargo:rustc-check-cfg=cfg(feature, values(\"deserialize_in_place\"))");
+
     // Sometimes on Windows the git checkout does not correctly wire up the
     // symlink from serde_derive_internals/src to serde_derive/src/internals.
     // When this happens we'll just build based on relative paths within the git
diff --git a/serde_derive_internals/lib.rs b/serde_derive_internals/lib.rs
index 1053b009ae..6edb07ee0c 100644
--- a/serde_derive_internals/lib.rs
+++ b/serde_derive_internals/lib.rs
@@ -1,4 +1,5 @@
-#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.29.0")]
+#![doc(html_root_url = "https://docs.rs/serde_derive_internals/0.29.1")]
+#![cfg_attr(not(check_cfg), allow(unexpected_cfgs))]
 // Ignored clippy lints
 #![allow(
     clippy::cognitive_complexity,
diff --git a/test_suite/tests/test_de_error.rs b/test_suite/tests/test_de_error.rs
index 75c7e30304..cae5eddaba 100644
--- a/test_suite/tests/test_de_error.rs
+++ b/test_suite/tests/test_de_error.rs
@@ -1524,7 +1524,6 @@ fn test_systemtime_overflow_struct() {
     );
 }
 
-#[cfg(systemtime_checked_add)]
 #[test]
 fn test_systemtime_overflow() {
     assert_de_tokens_error::<SystemTime>(