diff --git a/instaloader.py b/instaloader.py
index 79c7420..48e950b 100755
--- a/instaloader.py
+++ b/instaloader.py
@@ -701,7 +701,7 @@ class Instaloader:
                      filename_suffix: Optional[str] = None) -> bool:
         """Downloads and saves picture with given url under given directory with given timestamp.
         Returns true, if file was actually downloaded, i.e. updated."""
-        urlmatch = re.search('\\.[a-z]*\\?', url)
+        urlmatch = re.search('\\.[a-z0-9]*\\?', url)
         file_extension = url[-3:] if urlmatch is None else urlmatch.group(0)[1:-1]
         if filename_suffix is not None:
             filename += '_' + filename_suffix