diff --git a/src/calibre/ebooks/snb/snbml.py b/src/calibre/ebooks/snb/snbml.py
index af0106aaa0..1847e05a4b 100644
--- a/src/calibre/ebooks/snb/snbml.py
+++ b/src/calibre/ebooks/snb/snbml.py
@@ -25,7 +25,7 @@ def ProcessFileName(fileName):
     fileName = fileName.lower()
     # Change all images to jpg
     root, ext = os.path.splitext(fileName) 
-    if ext in [ '.jpeg', '.jpg', '.gif', '.svg' ]:
+    if ext in [ '.jpeg', '.jpg', '.gif', '.svg', '.png' ]:
         fileName = root + '.jpg'
     return fileName