diff --git a/mail2misp/mail2misp.py b/mail2misp/mail2misp.py
index d6deb6a..5ae34d0 100644
--- a/mail2misp/mail2misp.py
+++ b/mail2misp/mail2misp.py
@@ -95,7 +95,12 @@ class Mail2MISP():
     def _find_attached_forward(self):
         forwarded_emails = []
         for attachment in self.original_mail.iter_attachments():
-            attachment_content = attachment.get_content()
+            try:
+                attachment_content = attachment.get_content()
+            except KeyError:
+                # Attachment type has no handler
+                continue
+
             # Search for email forwarded as attachment
             # I could have more than one, attaching everything.
             if isinstance(attachment_content, message.EmailMessage):
diff --git a/tests/tests.py b/tests/tests.py
index 44391b9..a7a0280 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -82,6 +82,14 @@ class TestMailToMISP(unittest.TestCase):
         self.assertEqual(self.mail2misp.misp_event.analysis, '0')
         self.mail2misp.add_event()
 
+    def test_nested_mime(self):
+        config = importlib.import_module('tests.config_forward')
+        self.mail2misp = Mail2MISP('', '', '', config=config, offline=True)
+        with open('tests/mails/test_nested_mime.eml', 'rb') as f:
+            self.mail2misp.load_email(BytesIO(f.read()))
+        self.mail2misp.process_email_body()
+        self.assertEqual(self.mail2misp.clean_email_body, 'example.org\r\nwww.example.org\r\n')
+
     def test_attached_emails(self):
         config = importlib.import_module('tests.config_carrier')
         self.mail2misp = Mail2MISP('', '', '', config=config, offline=True)
@@ -89,5 +97,6 @@ class TestMailToMISP(unittest.TestCase):
             attached_emails = self.mail2misp.get_attached_emails(BytesIO(f.read()))
         self.assertEqual(len(attached_emails), 7)
 
+
 if __name__ == '__main__':
     unittest.main()