diff --git a/test/test_jsinterp.py b/test/test_jsinterp.py
index a8f312fde..1cc148b15 100644
--- a/test/test_jsinterp.py
+++ b/test/test_jsinterp.py
@@ -516,6 +516,9 @@ class TestJSInterpreter(unittest.TestCase):
         jsi = JSInterpreter('function x(){return 42 << NaN}')
         self.assertEqual(jsi.call_function('x'), 42)
 
+        jsi = JSInterpreter('function x(){return 42 << Infinity}')
+        self.assertEqual(jsi.call_function('x'), 42)
+
     def test_32066(self):
         jsi = JSInterpreter("function x(){return Math.pow(3, 5) + new Date('1970-01-01T08:01:42.000+08:00') / 1000 * -239 - -24205;}")
         self.assertEqual(jsi.call_function('x'), 70)
diff --git a/test/test_youtube_signature.py b/test/test_youtube_signature.py
index decf7ee38..d41d708a0 100644
--- a/test/test_youtube_signature.py
+++ b/test/test_youtube_signature.py
@@ -143,6 +143,14 @@ _NSIG_TESTS = [
         'https://www.youtube.com/s/player/dac945fd/player_ias.vflset/en_US/base.js',
         'o8BkRxXhuYsBCWi6RplPdP', '3Lx32v_hmzTm6A',
     ),
+    (
+        'https://www.youtube.com/s/player/6f20102c/player_ias.vflset/en_US/base.js',
+        'lE8DhoDmKqnmJJ', 'pJTTX6XyJP2BYw',
+    ),
+    (
+        'https://www.youtube.com/s/player/cfa9e7cb/player_ias.vflset/en_US/base.js',
+        'qO0NiMtYQ7TeJnfFG2', 'k9cuJDHNS5O7kQ',
+    ),
 ]
 
 
diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
index f837865c4..dc580943e 100644
--- a/youtube_dl/jsinterp.py
+++ b/youtube_dl/jsinterp.py
@@ -2,7 +2,6 @@ from __future__ import unicode_literals
 
 import itertools
 import json
-import math
 import operator
 import re
 
@@ -52,6 +51,10 @@ def wraps_op(op):
     return update_and_rename_wrapper
 
 
+# NB In principle NaN cannot be checked by membership.
+# Here all NaN values are actually this one, so _NaN is _NaN,
+# although _NaN != _NaN.
+
 _NaN = float('nan')
 
 
@@ -126,13 +129,8 @@ def _js_comp_op(op):
 
 def _js_ternary(cndn, if_true=True, if_false=False):
     """Simulate JS's ternary operator (cndn?if_true:if_false)"""
-    if cndn in (False, None, 0, '', JS_Undefined):
+    if cndn in (False, None, 0, '', JS_Undefined, _NaN):
         return if_false
-    try:
-        if math.isnan(cndn):  # NB: NaN cannot be checked by membership
-            return if_false
-    except TypeError:
-        pass
     return if_true