diff --git a/distros/ros2-overlay.nix b/distros/ros2-overlay.nix
index af5d87832a..5bce648903 100644
--- a/distros/ros2-overlay.nix
+++ b/distros/ros2-overlay.nix
@@ -93,7 +93,7 @@ rosSelf: rosSuper: with rosSelf.lib; {
 
   python-cmake-module = rosSuper.python-cmake-module.overrideAttrs ({ ... }: let
     python = rosSelf.python;
-    libExt = if self.stdenv.isDarwin then "dylib" else "so";
+    libExt = self.stdenv.hostPlatform.extensions.sharedLibrary;
   in {
     pythonExecutable = python.pythonOnBuildForHost.interpreter;
     pythonLibrary = "${python}/lib/lib${python.libPrefix}.${libExt}";