diff --git a/distros/ament-package-setup-hook.sh b/distros/ament-cmake-core-setup-hook.sh
similarity index 59%
rename from distros/ament-package-setup-hook.sh
rename to distros/ament-cmake-core-setup-hook.sh
index f9a37105d6..cf740d89c7 100644
--- a/distros/ament-package-setup-hook.sh
+++ b/distros/ament-cmake-core-setup-hook.sh
@@ -21,3 +21,11 @@ _findAmentPackages() {
   _amentPackagesSeen["$pkg"]=1
 }
 addEnvHooks "$hostOffset" _findAmentPackages
+
+_amentCmakeCorePreConfigureHook() {
+  # Don't create share/ament_index/resource_index/parent_prefix_path resource
+  # that contains references to all dependencies. This file isn't used with Nix
+  # and just bloats the closure.
+  cmakeFlags+=" -DAMENT_CMAKE_ENVIRONMENT_PARENT_PREFIX_PATH_GENERATION=OFF"
+}
+preConfigureHooks+=(_amentCmakeCorePreConfigureHook)
diff --git a/distros/distro-overlay.nix b/distros/distro-overlay.nix
index dda221eb7c..1e206e042a 100644
--- a/distros/distro-overlay.nix
+++ b/distros/distro-overlay.nix
@@ -24,8 +24,8 @@ let
   overrides = rosSelf: rosSuper: with rosSelf.lib; {
     # ROS package overrides/fixups
 
-    ament-package = rosSuper.ament-package.overrideAttrs ({ ... }: {
-      setupHook = ./ament-package-setup-hook.sh;
+    ament-cmake-core = rosSuper.ament-cmake-core.overrideAttrs ({ ... }: {
+      setupHook = ./ament-cmake-core-setup-hook.sh;
     });
 
     camera-calibration-parsers = patchBoostPython rosSuper.camera-calibration-parsers;
@@ -248,13 +248,9 @@ let
     rmw-implementation = rosSuper.rmw-implementation.overrideAttrs ({
       propagatedBuildInputs ? [], ...
     }: {
-      # Make sure all supported implementations are available to dependent
-      # packages. They are already part of the closure, so we might as well
-      # support them. This package could also be overriden to only support a
-      # single implementation to reduce closure size.
+      # The default implementation must be available to all dependent packages
+      # at build time.
       propagatedBuildInputs = with rosSelf; [
-        rmw-connext-cpp
-        rmw-cyclonedds-cpp
         rmw-fastrtps-cpp
       ] ++ propagatedBuildInputs;
     });
diff --git a/examples/ros2-basic.nix b/examples/ros2-basic.nix
index 020d40af97..c27dcc0ff8 100755
--- a/examples/ros2-basic.nix
+++ b/examples/ros2-basic.nix
@@ -10,7 +10,11 @@ mkShell {
         ros-environment
         ros2topic
         ros2node
+        geometry-msgs
+        rmw-fastrtps-dynamic-cpp
       ];
     })
   ];
+
+  RMW_IMPLEMENTATION = "rmw_fastrtps_dynamic_cpp";
 }