diff --git /usr/lib/python2.7/dist-packages/univention/admin/handlers/users/user.py /usr/lib/python2.7/dist-packages/univention/admin/handlers/users/user.py
index 3977b3ddb1..a1fb991f25 100644
--- /usr/lib/python2.7/dist-packages/univention/admin/handlers/users/user.py
+++ /usr/lib/python2.7/dist-packages/univention/admin/handlers/users/user.py
@@ -960,6 +960,10 @@ def load_certificate(user_certificate):
 		):
 			for key, attr in load_certificate.ATTR.items():
 				value = getattr(entity, key)
+				try:
+					value = value.decode('UTF-8')
+				except UnicodeError:
+					value = value.decode('UTF-8', 'replace').encode('UTF-8')
 				values[prefix + attr] = value
 	except (X509.X509Error, AttributeError):
 		return {}