diff --git a/src/NServiceBus.Core/Encryption/Rijndael/EncryptionService.cs b/src/NServiceBus.Core/Encryption/Rijndael/EncryptionService.cs
index fd17bf92077..7506f6f17bf 100644
--- a/src/NServiceBus.Core/Encryption/Rijndael/EncryptionService.cs
+++ b/src/NServiceBus.Core/Encryption/Rijndael/EncryptionService.cs
@@ -168,11 +168,7 @@ private string DecryptUsingKeyIdentifier(EncryptedValue encryptedValue, string k
 
         protected virtual void AddKeyIdentifierHeader()
         {
-            var headers = Bus.OutgoingHeaders;
-            if (!headers.ContainsKey(Headers.RijndaelKeyIdentifier))
-            {
-                headers.Add(Headers.RijndaelKeyIdentifier, EncryptionKeyIdentifier);
-            }
+            Bus.OutgoingHeaders[Headers.RijndaelKeyIdentifier] = EncryptionKeyIdentifier;
         }
 
         protected virtual bool TryGetKeyIdentifierHeader(out string keyIdentifier)