diff --git a/src/libprs500/ebooks/lrf/any/convert_from.py b/src/libprs500/ebooks/lrf/any/convert_from.py
index 7b4af29a45..0d4b88d521 100644
--- a/src/libprs500/ebooks/lrf/any/convert_from.py
+++ b/src/libprs500/ebooks/lrf/any/convert_from.py
@@ -139,7 +139,7 @@ def process_file(path, options, logger=None):
         elif ext in ['mobi', 'prc']:
             convertor = mobi2lrf
         if not convertor:
-            raise UnknownFormatError('Coverting from %s to LRF is not supported.')
+            raise UnknownFormatError('Coverting from %s to LRF is not supported.'%ext)
         convertor(path, options, logger)
     finally:
         os.chdir(cwd)