diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index 43fd390..6dfbfd1 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -751,7 +751,10 @@
 	}
 	if timestamp := proptools.String(f.properties.Fake_timestamp); timestamp != "" {
 		addStr("timestamp", timestamp)
+	} else if ctx.Config().Getenv("USE_FIXED_TIMESTAMP_IMG_FILES") == "true" {
+		addStr("use_fixed_timestamp", "true")
 	}
+
 	if uuid := proptools.String(f.properties.Uuid); uuid != "" {
 		addStr("uuid", uuid)
 		addStr("hash_seed", uuid)