diff --git a/EnvelopeGenerator.Application/Services/EnvelopeGeneratorExtensions.cs b/EnvelopeGenerator.Application/Services/EnvelopeGeneratorExtensions.cs
index 7eb3e9cd..a384e2db 100644
--- a/EnvelopeGenerator.Application/Services/EnvelopeGeneratorExtensions.cs
+++ b/EnvelopeGenerator.Application/Services/EnvelopeGeneratorExtensions.cs
@@ -90,13 +90,13 @@
         /// </summary>
         /// <param name="envelopeReceiverId">The base64 encoded string to decode.</param>
         /// <returns>The envelope UUID.</returns>
-        public static string GetEnvelopeUuid(this string envelopeReceiverId) => envelopeReceiverId.DecodeEnvelopeReceiverId().EnvelopeUuid;
+        public static string? GetEnvelopeUuid(this string envelopeReceiverId) => envelopeReceiverId.DecodeEnvelopeReceiverId().EnvelopeUuid;
 
         /// <summary>
         /// Gets the receiver signature from the decoded envelope receiver ID.
         /// </summary>
         /// <param name="envelopeReceiverId">The base64 encoded string to decode.</param>
         /// <returns>The receiver signature.</returns>
-        public static string GetReceiverSignature(this string envelopeReceiverId) => envelopeReceiverId.DecodeEnvelopeReceiverId().ReceiverSignature;
+        public static string? GetReceiverSignature(this string envelopeReceiverId) => envelopeReceiverId.DecodeEnvelopeReceiverId().ReceiverSignature;
     }
 }
\ No newline at end of file