diff --git a/cps/helper.py b/cps/helper.py
index 562d09af..e7b0a28e 100755
--- a/cps/helper.py
+++ b/cps/helper.py
@@ -80,7 +80,7 @@ def make_mobi(book_id, calibrepath):
 
     file_path = os.path.join(calibrepath, book.path, data.name)
     if os.path.exists(file_path + u".epub"):
-        p = subprocess.Popen((kindlegen + " \"" + file_path + u".epub\" ").encode(sys.getfilesystemencoding()),
+        p = subprocess.Popen((kindlegen + " \"" + file_path + u".epub\"").encode(sys.getfilesystemencoding()),
                              stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         # Poll process for new output until finished
         while True: