diff --git a/mbox2web b/mbox2web
index 5d11e25..0b5f2ec 100755
--- a/mbox2web
+++ b/mbox2web
@@ -93,7 +93,7 @@ def render_body(msg):
         parts = msg.get_payload()
         if type(parts) == str:
             # mislabelled, assume text/plain
-            raise NotImplementedError()
+            return render_text_plain(msg)
         partshtml = []
         for part in msg.get_payload():
             partshtml.append(render_body(part))