diff --git a/Duplicati/Library/Backend/S3/S3Backend.cs b/Duplicati/Library/Backend/S3/S3Backend.cs
index f96c3c94c..ec7b5d9ab 100644
--- a/Duplicati/Library/Backend/S3/S3Backend.cs
+++ b/Duplicati/Library/Backend/S3/S3Backend.cs
@@ -343,7 +343,7 @@ namespace Duplicati.Library.Backend
                     new CommandLineArgument(SERVER_NAME, CommandLineArgument.ArgumentType.String, Strings.S3Backend.S3ServerNameDescriptionShort, Strings.S3Backend.S3ServerNameDescriptionLong(hostnames.ToString()), DEFAULT_S3_HOST),
                     new CommandLineArgument(LOCATION_OPTION, CommandLineArgument.ArgumentType.String, Strings.S3Backend.S3LocationDescriptionShort, Strings.S3Backend.S3LocationDescriptionLong(locations.ToString())),
                     new CommandLineArgument(SSL_OPTION, CommandLineArgument.ArgumentType.Boolean, Strings.S3Backend.DescriptionUseSSLShort, Strings.S3Backend.DescriptionUseSSLLong),
-                    new CommandLineArgument(S3_CLIENT_OPTION, CommandLineArgument.ArgumentType.Enumeration, Strings.S3Backend.S3ClientDescriptionShort, Strings.S3Backend.S3ClientDescriptionLong, "aws", new string[] { "aws", "minio" }),
+                    new CommandLineArgument(S3_CLIENT_OPTION, CommandLineArgument.ArgumentType.Enumeration, Strings.S3Backend.S3ClientDescriptionShort, Strings.S3Backend.S3ClientDescriptionLong, "aws", null, new string[] { "aws", "minio" }),
                     new CommandLineArgument(S3_DISABLE_CHUNK_ENCODING_OPTION, CommandLineArgument.ArgumentType.Boolean, Strings.S3Backend.DescriptionDisableChunkEncodingShort, Strings.S3Backend.DescriptionDisableChunkEncodingLong, "false"),
                     new CommandLineArgument("auth-password", CommandLineArgument.ArgumentType.Password, Strings.S3Backend.AuthPasswordDescriptionShort, Strings.S3Backend.AuthPasswordDescriptionLong),
                     new CommandLineArgument("auth-username", CommandLineArgument.ArgumentType.String, Strings.S3Backend.AuthUsernameDescriptionShort, Strings.S3Backend.AuthUsernameDescriptionLong),