diff --git a/helper/bwrap/config.go b/helper/bwrap/config.go
index 9e15a29..5556f4c 100644
--- a/helper/bwrap/config.go
+++ b/helper/bwrap/config.go
@@ -52,7 +52,7 @@ type Config struct {
 	LockFile []string `json:"lock_file,omitempty"`
 
 	// ordered filesystem args
-	Filesystem []FSBuilder
+	Filesystem []FSBuilder `json:"filesystem,omitempty"`
 
 	// change permissions (must already exist)
 	// (--chmod OCTAL PATH)