diff --git a/CMakeLists.txt b/CMakeLists.txt
index fc198b7..420a445 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -314,36 +314,39 @@ install(EXPORT qtty_cppTargets
 
 # ---------------------------------------------------------------------------
 # Packaging (CPack — DEB and RPM)
+# Only define package metadata when qtty-cpp is the top-level project.
 # ---------------------------------------------------------------------------
-set(CPACK_PACKAGE_NAME             "qtty-cpp")
-set(CPACK_PACKAGE_VERSION          "${PROJECT_VERSION}")
-set(CPACK_PACKAGE_VENDOR           "Siderust")
-set(CPACK_PACKAGE_CONTACT          "VPRamon <vallespuigramon@gmail.com>")
-set(CPACK_PACKAGE_DESCRIPTION_SUMMARY
-    "C++ wrapper for the qtty unit-safe physical quantities library")
-set(CPACK_PACKAGE_DESCRIPTION
-    "qtty-cpp provides a header-only C++17 API over the qtty Rust\n"
-    "quantities library via the qtty-ffi C ABI.  It bundles the pre-built\n"
-    "shared library (qtty_ffi) together with the C++ headers and CMake\n"
-    "package config.")
-set(CPACK_RESOURCE_FILE_LICENSE    "${CMAKE_CURRENT_SOURCE_DIR}/LICENSE")
-set(CPACK_PACKAGE_HOMEPAGE_URL     "https://github.com/Siderust/qtty-cpp")
-
-# -- DEB -----------------------------------------------------------------------
-set(CPACK_DEBIAN_PACKAGE_MAINTAINER "VPRamon <vallespuigramon@gmail.com>")
-set(CPACK_DEBIAN_PACKAGE_SECTION    "libs")
-set(CPACK_DEBIAN_PACKAGE_DEPENDS    "libc6 (>= 2.17), libstdc++6 (>= 9)")
-set(CPACK_DEBIAN_FILE_NAME          DEB-DEFAULT)
-
-# -- RPM -----------------------------------------------------------------------
-set(CPACK_RPM_PACKAGE_LICENSE    "AGPL-3.0")
-set(CPACK_RPM_PACKAGE_GROUP      "Development/Libraries")
-set(CPACK_RPM_PACKAGE_REQUIRES   "glibc >= 2.17, libstdc++ >= 9")
-set(CPACK_RPM_FILE_NAME          RPM-DEFAULT)
-
-set(CPACK_GENERATOR "DEB;RPM")
-
-include(CPack)
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+    set(CPACK_PACKAGE_NAME             "qtty-cpp")
+    set(CPACK_PACKAGE_VERSION          "${PROJECT_VERSION}")
+    set(CPACK_PACKAGE_VENDOR           "Siderust")
+    set(CPACK_PACKAGE_CONTACT          "VPRamon <vallespuigramon@gmail.com>")
+    set(CPACK_PACKAGE_DESCRIPTION_SUMMARY
+        "C++ wrapper for the qtty unit-safe physical quantities library")
+    set(CPACK_PACKAGE_DESCRIPTION
+        "qtty-cpp provides a header-only C++17 API over the qtty Rust\n"
+        "quantities library via the qtty-ffi C ABI.  It bundles the pre-built\n"
+        "shared library (qtty_ffi) together with the C++ headers and CMake\n"
+        "package config.")
+    set(CPACK_RESOURCE_FILE_LICENSE    "${CMAKE_CURRENT_SOURCE_DIR}/LICENSE")
+    set(CPACK_PACKAGE_HOMEPAGE_URL     "https://github.com/Siderust/qtty-cpp")
+
+    # -- DEB -------------------------------------------------------------------
+    set(CPACK_DEBIAN_PACKAGE_MAINTAINER "VPRamon <vallespuigramon@gmail.com>")
+    set(CPACK_DEBIAN_PACKAGE_SECTION    "libs")
+    set(CPACK_DEBIAN_PACKAGE_DEPENDS    "libc6 (>= 2.17), libstdc++6 (>= 9)")
+    set(CPACK_DEBIAN_FILE_NAME          DEB-DEFAULT)
+
+    # -- RPM -------------------------------------------------------------------
+    set(CPACK_RPM_PACKAGE_LICENSE    "AGPL-3.0")
+    set(CPACK_RPM_PACKAGE_GROUP      "Development/Libraries")
+    set(CPACK_RPM_PACKAGE_REQUIRES   "glibc >= 2.17, libstdc++ >= 9")
+    set(CPACK_RPM_FILE_NAME          RPM-DEFAULT)
+
+    set(CPACK_GENERATOR "DEB;RPM")
+
+    include(CPack)
+endif()
 
 # Generate unit files (if needed)
 add_custom_target(