diff --git a/plugins/diff/erofs/differ_linux.go b/plugins/diff/erofs/differ_linux.go
index 83cb9f844..f84115258 100644
--- a/plugins/diff/erofs/differ_linux.go
+++ b/plugins/diff/erofs/differ_linux.go
@@ -76,8 +76,8 @@ func NewErofsDiffer(store content.Store, mkfsExtraOpts []string) differ {
 // Since `images.DiffCompression` doesn't support arbitrary media types,
 // disallow non-empty suffixes for now.
 func isErofsMediaType(mt string) bool {
-	mediaType, ext, ok := strings.Cut(mt, "+")
-	if !ok || ext != "" {
+	mediaType, _, hasExt := strings.Cut(mt, "+")
+	if hasExt {
 		return false
 	}
 	return strings.HasSuffix(mediaType, ".erofs")