diff --git a/src/FrostFS.SDK.Client/Tools/RequestSigner.cs b/src/FrostFS.SDK.Client/Tools/RequestSigner.cs
index 80dfae7..e2aceef 100644
--- a/src/FrostFS.SDK.Client/Tools/RequestSigner.cs
+++ b/src/FrostFS.SDK.Client/Tools/RequestSigner.cs
@@ -1,5 +1,4 @@
 using System;
-using System.IO;
 using System.Security.Cryptography;
 
 using FrostFS.Refs;
@@ -14,7 +13,6 @@ using Org.BouncyCastle.Crypto.Digests;
 using Org.BouncyCastle.Crypto.Parameters;
 using Org.BouncyCastle.Crypto.Signers;
 using Org.BouncyCastle.Math;
-using Org.BouncyCastle.Utilities;
 using Signature = FrostFS.Refs.Signature;
 
 namespace FrostFS.SDK.Client;
@@ -106,18 +104,7 @@ public static class RequestSigner
 
     internal static Signature SignMessagePart(this ClientKey key, IMessage? data)
     {
-        if (data is null)
-        {
-            return new Signature
-            {
-                Key = key.PublicKeyProto,
-                Sign = key.ECDsaKey.SignData(ReadOnlyMemory<byte>.Empty),
-            };
-        }
-
-        var size = data.CalculateSize();
-
-        if (size == 0)
+        if (data is null || data.CalculateSize() == 0)
         {
             return new Signature
             {