--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,6 +6,8 @@ cmake_minimum_required(VERSION 3.21)
 # (ALSA::ALSA new in 3.12 and used in pm_common/CMakeLists.txt)
 # Some Java stuff failed on 3.17 but works with 3.20+
 
+include(GNUInstallDirs)
+
 cmake_policy(SET CMP0091 NEW) # enables MSVC_RUNTIME_LIBRARY target property
 
 # Previously, PortMidi versions were simply SVN commit version numbers.