--- modules/squish/SCsub.orig	2019-03-23 11:07:40 UTC
+++ modules/squish/SCsub
@@ -22,7 +22,7 @@ if env['builtin_squish']:
 
     thirdparty_sources = [thirdparty_dir + file for file in thirdparty_sources]
 
-    env_squish.Append(CPPPATH=[thirdparty_dir])
+    env_squish.Prepend(CPPPATH=[thirdparty_dir])
 
     env_thirdparty = env_squish.Clone()
     env_thirdparty.disable_warnings()