diff --git a/mkspecs/features/vatsim.pri b/mkspecs/features/vatsim.pri
index 30e5ce641..2ec930a7c 100644
--- a/mkspecs/features/vatsim.pri
+++ b/mkspecs/features/vatsim.pri
@@ -2,10 +2,10 @@
 
 # VATSIM client id as assigned by VATSIM Network team. The one below is a test key.
 # It is working only with VATGER test server.
-VATSIM_CLIENT_ID = "0xb9ba"
+isEmpty(VATSIM_CLIENT_ID):VATSIM_CLIENT_ID = "0xb9ba"
 
 # VATSIM private key, which belongs to the id above.
-VATSIM_CLIENT_PRIVATE_KEY = "727d1efd5cb9f8d2c28372469d922bb4"
+isEmpty(VATSIM_CLIENT_PRIVATE_KEY):VATSIM_CLIENT_PRIVATE_KEY = "727d1efd5cb9f8d2c28372469d922bb4"
 
 # Comment the section below to build a version without VATSIM features enabled
 BLACK_CONFIG *= SwiftVatsimSupport