diff --git a/src/you_get/extractors/youtube.py b/src/you_get/extractors/youtube.py
index 81b45ac5..4e5e0f60 100644
--- a/src/you_get/extractors/youtube.py
+++ b/src/you_get/extractors/youtube.py
@@ -78,6 +78,7 @@ class YouTube(VideoExtractor):
         # - https://www.youtube.com/yts/jsbin/player_ias-vfl-jbnrr/da_DK/base.js
         # - https://www.youtube.com/s/player/0b643cd1/player_ias.vflset/sv_SE/base.js
         # - https://www.youtube.com/s/player/50e823fc/player_ias.vflset/sv_SE/base.js
+        # - https://www.youtube.com/s/player/3b5d5649/player_ias.vflset/sv_SE/base.js
         def tr_js(code):
             code = re.sub(r'function', r'def', code)
             # add prefix '_sig_' to prevent namespace pollution
@@ -117,7 +118,9 @@ class YouTube(VideoExtractor):
             f2 = re.sub(r'\$', '_dollar', f2)
             code = code + 'global _sig_%s\n' % f2 + tr_js(f2def)
 
-        f1 = re.sub(r'(as|if|in|is|or)', r'_\1', f1)
+        # if f1 contains more than 2 characters, no need to do substitution
+        # FIXME: we probably shouldn't do any substitution here at all?
+        f1 = re.sub(r'^(as|if|in|is|or)$', r'_\1', f1)
         f1 = re.sub(r'\$', '_dollar', f1)
         code = code + '_sig=_sig_%s(s)' % f1
         exec(code, globals(), locals())