diff --git a/cmake/start_options.cmake b/cmake/start_options.cmake
index f3494cfd9..d9699a1bb 100644
--- a/cmake/start_options.cmake
+++ b/cmake/start_options.cmake
@@ -25,8 +25,9 @@ add_definitions(-DQET_ALLOW_OVERRIDE_CTBTD_OPTION)
 # Comment the line below to deactivate the --config-dir option
 add_definitions(-DQET_ALLOW_OVERRIDE_CD_OPTION)
 
-# Comment the line below to deactivate the --data-dir option
-add_definitions(-DQET_ALLOW_OVERRIDE_DD_OPTION)
+# Enable project database export when requested by the build system.
+option(QET_EXPORT_PROJECT_DB "Enable project database export" OFF)
 
-#comment the line below to disable the project database export
-#add_definitions(-DQET_EXPORT_PROJECT_DB) #error Todo
+if(QET_EXPORT_PROJECT_DB)
+    add_compile_definitions(QET_EXPORT_PROJECT_DB)
+endif()