diff --git a/src/calibre/library/cli.py b/src/calibre/library/cli.py
index b2f80e9ac6..ab7a4ade69 100644
--- a/src/calibre/library/cli.py
+++ b/src/calibre/library/cli.py
@@ -619,7 +619,7 @@ def catalog_option_parser(args):
     
         # Validate plugin exists for specified output format
         output = os.path.abspath(args[0])
-        file_extension = output[output.rfind('.') + 1:]
+        file_extension = output[output.rfind('.') + 1:].lower()
         
         if not file_extension in available_catalog_formats():
             print_help(parser, log)
@@ -633,7 +633,7 @@ def catalog_option_parser(args):
     log = Log()
     parser = get_parser(_(
     '''
-    %prog catalog /path/to/destination.(epub|csv|xml|...) [options]
+    %prog catalog /path/to/destination.(csv|epub|mobi|xml ...) [options]
     
     Export a catalog in format specified by path/to/destination extension.
     Options control how entries are displayed in the generated catalog ouput.