diff --git a/Source/AaxDecrypter/AaxcDownloadConvertBase.cs b/Source/AaxDecrypter/AaxcDownloadConvertBase.cs
index 1b309e59..3975e8af 100644
--- a/Source/AaxDecrypter/AaxcDownloadConvertBase.cs
+++ b/Source/AaxDecrypter/AaxcDownloadConvertBase.cs
@@ -32,7 +32,11 @@ namespace AaxDecrypter
 		protected bool Step_GetMetadata()
 		{
 			AaxFile = new AaxFile(InputFileStream);
-			AaxFile.SetDecryptionKey(DownloadOptions.AudibleKey, DownloadOptions.AudibleIV);
+
+			if (DownloadOptions.AudibleKey?.Length == 8 && DownloadOptions.AudibleIV is null)
+				AaxFile.SetDecryptionKey(DownloadOptions.AudibleKey);
+			else
+				AaxFile.SetDecryptionKey(DownloadOptions.AudibleKey, DownloadOptions.AudibleIV);
 
 			if (DownloadOptions.StripUnabridged)
 			{
diff --git a/Source/AaxDecrypter/AudiobookDownloadBase.cs b/Source/AaxDecrypter/AudiobookDownloadBase.cs
index 9f8bb535..91883c09 100644
--- a/Source/AaxDecrypter/AudiobookDownloadBase.cs
+++ b/Source/AaxDecrypter/AudiobookDownloadBase.cs
@@ -182,7 +182,6 @@ namespace AaxDecrypter
 			FileUtility.SaferDelete(jsonDownloadState);
 
 			if (!string.IsNullOrEmpty(DownloadOptions.AudibleKey) &&
-				!string.IsNullOrEmpty(DownloadOptions.AudibleIV) &&
 				DownloadOptions.RetainEncryptedFile)
 			{
 				string aaxPath = Path.ChangeExtension(tempFilePath, ".aax");