diff --git a/django/utils/translation/trans_real.py b/django/utils/translation/trans_real.py
index a6b7eaa489..c7b41fa373 100644
--- a/django/utils/translation/trans_real.py
+++ b/django/utils/translation/trans_real.py
@@ -668,7 +668,10 @@ def parse_accept_lang_header(lang_string):
         if first:
             return []
         if priority:
-            priority = float(priority)
+            try:
+                priority = float(priority)
+            except ValueError:
+                return []
         if not priority:        # if priority is 0.0 at this point make it 1.0
             priority = 1.0
         result.append((lang, priority))
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index c18c88cad3..f482dba3bb 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -849,6 +849,7 @@ class MiscTests(TransRealMixin, TestCase):
         self.assertEqual([], p('de;q=0.a'))
         self.assertEqual([], p('12-345'))
         self.assertEqual([], p(''))
+        self.assertEqual([], p('en; q=1,'))
 
     def test_parse_literal_http_header(self):
         """