diff --git a/src/kemal/helpers/helpers.cr b/src/kemal/helpers/helpers.cr
index 7e55681..87c8947 100644
--- a/src/kemal/helpers/helpers.cr
+++ b/src/kemal/helpers/helpers.cr
@@ -156,7 +156,7 @@ private def multipart(file, env : HTTP::Server::Context)
     env.response.status_code = 206
     env.response.content_length = endb - startb
     env.response.headers["Accept-Ranges"] = "bytes"
-    env.response.headers["Content-Range"] = "bytes #{startb}-#{endb - 1}/#{fileb}" # MUST
+    env.response.headers["Content-Range"] = "bytes #{startb}-#{endb > 1 ? endb - 1 : 1}/#{fileb}" # MUST
 
     if startb > 1024
       skipped = 0