diff --git a/r2r/build.rs b/r2r/build.rs
index 61465ebd8..ec3ce513d 100644
--- a/r2r/build.rs
+++ b/r2r/build.rs
@@ -36,6 +36,18 @@ use filenames::*;
 
 fn main() {
     r2r_common::print_cargo_watches();
+    // Declare all the custom cfg directives we use
+    // to silence cargo warnings.
+    r2r_common::print_cargo_used_cfgs(&[
+        "r2r__rosgraph_msgs__msg__Clock",
+        "r2r__action_msgs__msg__GoalStatus",
+        "r2r__test_msgs__msg__Defaults",
+        "r2r__test_msgs__msg__Arrays",
+        "r2r__test_msgs__msg__WStrings",
+        "r2r__example_interfaces__srv__AddTwoInts",
+        "r2r__std_srvs__srv__Empty",
+        "r2r__example_interfaces__action__Fibonacci",
+    ]);
     r2r_common::print_cargo_ros_distro();
 
     let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
diff --git a/r2r_common/src/lib.rs b/r2r_common/src/lib.rs
index ffe30b08f..36f333a7b 100644
--- a/r2r_common/src/lib.rs
+++ b/r2r_common/src/lib.rs
@@ -150,6 +150,19 @@ pub fn print_cargo_ros_distro() {
     }
 }
 
+pub fn print_cargo_used_cfgs(message_cfgs: &[&str]) {
+    // Declare all supported ros distros as cfg directives for cargo
+    for d in SUPPORTED_ROS_DISTROS {
+        println!("cargo::rustc-check-cfg=cfg(r2r__ros__distro__{d})");
+    }
+
+    // additionally we have conditional tests and features based on some
+    // optional ros message packages.
+    for c in message_cfgs {
+        println!("cargo::rustc-check-cfg=cfg({c})");
+    }
+}
+
 pub fn print_cargo_link_search() {
     let ament_prefix_var_name = "AMENT_PREFIX_PATH";
     if let Some(paths) = env::var_os(ament_prefix_var_name) {
diff --git a/r2r_rcl/src/lib.rs b/r2r_rcl/src/lib.rs
index efb189ed3..9a3348647 100644
--- a/r2r_rcl/src/lib.rs
+++ b/r2r_rcl/src/lib.rs
@@ -3,6 +3,10 @@
 #![allow(non_snake_case)]
 #![allow(improper_ctypes)]
 #![allow(dead_code)]
+// Silence "`extern` fn uses type `u128`, which is not FFI-safe"
+// As of rustc 1.78, this has been fixed.
+// It could be good to still warn if building with an older rust version.
+#![allow(improper_ctypes)]
 include!(concat!(env!("OUT_DIR"), "/rcl_bindings.rs"));
 
 use std::ffi::{CStr, CString};
diff --git a/tests/build_minimal_node.bash b/tests/build_minimal_node.bash
index a478386e9..bf38e6dce 100755
--- a/tests/build_minimal_node.bash
+++ b/tests/build_minimal_node.bash
@@ -1,6 +1,7 @@
 #!/bin/bash
 
 # Use the local version of r2r when building the minimal node.
+rm /r2r/r2r_minimal_node/r2r_minimal_node/Cargo.lock
 cat >> /r2r/r2r_minimal_node/r2r_minimal_node/Cargo.toml << EOF
 
 [patch.crates-io]