diff --git a/apps/converter/api.py b/apps/converter/api.py
index 7e22354b2d..2c3269fab9 100644
--- a/apps/converter/api.py
+++ b/apps/converter/api.py
@@ -15,7 +15,7 @@ from .literals import (TRANSFORMATION_CHOICES, TRANSFORMATION_RESIZE,
     FILE_FORMATS)
 from .utils import cleanup
 from .runtime import office_converter
-from .exceptions import OfficeConversionError
+from .exceptions import OfficeConversionError, UnknownFileFormat
 
 HASH_FUNCTION = lambda x: hashlib.sha256(x).hexdigest()