diff --git a/ECMConfig.cmake.in b/ECMConfig.cmake.in
--- a/ECMConfig.cmake.in
+++ b/ECMConfig.cmake.in
@@ -6,6 +6,8 @@
 
 set(ECM_KDE_MODULE_DIR "@PACKAGE_KDE_MODULES_INSTALL_DIR@")
 
+set(ECM_PREFIX "${PACKAGE_PREFIX_DIR}")
+
 set(ECM_MODULE_PATH "${ECM_MODULE_DIR}" "${ECM_FIND_MODULE_DIR}" "${ECM_KDE_MODULE_DIR}")
 
 set(ECM_GLOBAL_FIND_VERSION "${ECM_FIND_VERSION}")
diff --git a/kde-modules/KDEInstallDirs.cmake b/kde-modules/KDEInstallDirs.cmake
--- a/kde-modules/KDEInstallDirs.cmake
+++ b/kde-modules/KDEInstallDirs.cmake
@@ -426,7 +426,10 @@
         BUNDLE_INSTALL_DIR)
 endif()
 
-
+# Only supported since cmake 3.7
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+    set(CMAKE_INSTALL_PREFIX "${ECM_PREFIX}" CACHE PATH "Install path prefix" FORCE)
+endif()
 
 _define_absolute(EXECROOTDIR ""
     "executables and libraries"