diff --git a/cc/cc.go b/cc/cc.go
index 037b99c..4ed27f4 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -378,7 +378,7 @@
 
 type specifiedDeps struct {
 	sharedLibs       []string
-	systemSharedLibs []string
+	systemSharedLibs []string // Note nil and [] are semantically distinct.
 }
 
 type installer interface {