diff --git a/youtube_dl/extractor/gfycat.py b/youtube_dl/extractor/gfycat.py
index 884700c52b..45ccc11c10 100644
--- a/youtube_dl/extractor/gfycat.py
+++ b/youtube_dl/extractor/gfycat.py
@@ -82,7 +82,7 @@ def _real_extract(self, url):
             video_url = gfy.get('%sUrl' % format_id)
             if not video_url:
                 continue
-            filesize = gfy.get('%sSize' % format_id)
+            filesize = int_or_none(gfy.get('%sSize' % format_id))
             formats.append({
                 'url': video_url,
                 'format_id': format_id,