diff --git a/cmd_export_attachments.go b/cmd_export_attachments.go
index 8e38197..66e6364 100644
--- a/cmd_export_attachments.go
+++ b/cmd_export_attachments.go
@@ -156,6 +156,10 @@ func cmdExportAttachments(args []string) cmdStatus {
 		}
 	}
 
+	if err := addContentTypes(); err != nil {
+		log.Print(err)
+	}
+
 	var ctx *signal.Context
 	if key == nil {
 		ctx, err = signal.Open(signalDir)
diff --git a/mime.go b/mime.go
index e8f8555..d0abcfa 100644
--- a/mime.go
+++ b/mime.go
@@ -46,6 +46,10 @@ func unveilMimeFiles() error {
 	return nil
 }
 
+func addContentTypes() error {
+	return mime.AddExtensionType(".aac", "audio/aac")
+}
+
 func extensionFromContentType(contentType string) (string, error) {
 	// Avoid silly results, such as .jpe for image/jpeg
 	switch t, _, _ := strings.Cut(contentType, ";"); t {