diff --git a/cc/cc.go b/cc/cc.go
index 312e42b..c532e50 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -125,7 +125,7 @@
 
 	// Everything in this list is a crime against abstraction and dependency tracking.
 	// Do not add anything to this list.
-	pctx.PrefixedPathsForSourceVariable("commonGlobalIncludes", "-isystem ",
+	pctx.PrefixedPathsForOptionalSourceVariable("commonGlobalIncludes", "-isystem ",
 		[]string{
 			"system/core/include",
 			"hardware/libhardware/include",