diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 81823ab..c2e2be7 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -6,15 +6,24 @@
 # SPDX-License-Identifier: Apache-2.0
 # ~~~
 
-# Test add_subdirectory suppport
-add_test(NAME integration.add_subdirectory
+# Test add_subdirectory suppport for headers
+add_test(NAME integration.add_subdirectory_headers
     COMMAND ${CMAKE_CTEST_COMMAND}
         --build-and-test ${CMAKE_CURRENT_LIST_DIR}/integration
-                         ${CMAKE_CURRENT_BINARY_DIR}/add_subdirectory
+                         ${CMAKE_CURRENT_BINARY_DIR}/add_subdirectory_headers
         --build-generator ${CMAKE_GENERATOR}
         --build-options -DFIND_PACKAGE_TESTING=OFF -DVULKAN_HEADERS_ENABLE_MODULE=OFF
 )
 
+# Test add_subdirectory suppport for C++20 modules
+add_test(NAME integration.add_subdirectory_modules
+    COMMAND ${CMAKE_CTEST_COMMAND}
+        --build-and-test ${CMAKE_CURRENT_LIST_DIR}/integration
+                         ${CMAKE_CURRENT_BINARY_DIR}/add_subdirectory_modules
+        --build-generator ${CMAKE_GENERATOR}
+        --build-options -DFIND_PACKAGE_TESTING=OFF -DVULKAN_HEADERS_ENABLE_MODULE=ON
+)
+
 set(test_install_dir "${CMAKE_CURRENT_BINARY_DIR}/install")
 add_test(NAME integration.install
     COMMAND ${CMAKE_COMMAND} --install ${VULKAN_HEADERS_BINARY_DIR} --prefix ${test_install_dir} --config $<CONFIG>
diff --git a/tests/integration/CMakeLists.txt b/tests/integration/CMakeLists.txt
index a641fd2..f426ed9 100644
--- a/tests/integration/CMakeLists.txt
+++ b/tests/integration/CMakeLists.txt
@@ -18,6 +18,9 @@ endif()
 if (NOT TARGET Vulkan::Headers)
     message(FATAL_ERROR "Vulkan::Headers target not defined")
 endif()
+if (NOT TARGET Vulkan::HppModule AND VULKAN_HEADERS_ENABLE_MODULE)
+    message(FATAL_ERROR "Vulkan::HppModule target not defined")
+endif()
 
 if (FIND_PACKAGE_TESTING)
     if (NOT DEFINED VulkanHeaders_VERSION)
@@ -37,6 +40,9 @@ if (NOT FIND_PACKAGE_TESTING)
     if (NOT TARGET Vulkan-Headers)
         message(FATAL_ERROR "Backcompat for Vulkan-Headers target broken!")
     endif()
+    if (NOT TARGET Vulkan-HppModule AND VULKAN_HEADERS_ENABLE_MODULE)
+        message(FATAL_ERROR "Backcompat for Vulkan-HppModule target broken!")
+    endif()
 endif()
 
 set(CMAKE_C_STANDARD 99)