diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 50326803d..2fe9cf585 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -2267,7 +2267,7 @@ def js_to_json(code):
         "(?:[^"\\]*(?:\\\\|\\['"nurtbfx/\n]))*[^"\\]*"|
         '(?:[^'\\]*(?:\\\\|\\['"nurtbfx/\n]))*[^'\\]*'|
         {comment}|,(?={skip}[\]}}])|
-        (?<![0-9])[a-zA-Z_][.a-zA-Z_0-9]*|
+        (?:(?<![0-9])[eE]|[a-df-zA-DF-Z_])[.a-zA-Z_0-9]*|
         \b(?:0[xX][0-9a-fA-F]+|0+[0-7]+)(?:{skip}:)?|
         [0-9]+(?={skip}:)
         '''.format(comment=COMMENT_RE, skip=SKIP_RE), fix_kv, code)