diff --git a/django/views/i18n.py b/django/views/i18n.py
index c8cc5d043f..c3a813b0fe 100644
--- a/django/views/i18n.py
+++ b/django/views/i18n.py
@@ -253,7 +253,7 @@ def get_javascript_catalog(locale, domain, packages):
         else:
             raise TypeError(key)
     for k, v in pdict.items():
-        catalog[k] = [v.get(i, '') for i in range(maxcnts[msgid] + 1)]
+        catalog[k] = [v.get(i, '') for i in range(maxcnts[k] + 1)]
 
     return catalog, plural
 
@@ -401,7 +401,7 @@ class JavaScriptCatalog(View):
             else:
                 raise TypeError(key)
         for k, v in pdict.items():
-            catalog[k] = [v.get(i, '') for i in range(maxcnts[msgid] + 1)]
+            catalog[k] = [v.get(i, '') for i in range(maxcnts[k] + 1)]
         return catalog
 
     def get_context_data(self, **kwargs):
diff --git a/docs/releases/1.10.5.txt b/docs/releases/1.10.5.txt
index ac9270c3c0..381f956bc8 100644
--- a/docs/releases/1.10.5.txt
+++ b/docs/releases/1.10.5.txt
@@ -11,3 +11,6 @@ Bugfixes
 
 * Fixed a crash in the debug view if ``request.user`` can't be retrieved, such
   as if the database is unavailable (:ticket:`27567`).
+
+* Fixed occasional missing plural forms in ``JavaScriptCatalog``
+  (:ticket:`27418`).
diff --git a/tests/view_tests/locale/pt/LC_MESSAGES/djangojs.mo b/tests/view_tests/locale/pt/LC_MESSAGES/djangojs.mo
new file mode 100644
index 0000000000..8407e242fc
Binary files /dev/null and b/tests/view_tests/locale/pt/LC_MESSAGES/djangojs.mo differ
diff --git a/tests/view_tests/locale/pt/LC_MESSAGES/djangojs.po b/tests/view_tests/locale/pt/LC_MESSAGES/djangojs.po
new file mode 100644
index 0000000000..ca643162e9
--- /dev/null
+++ b/tests/view_tests/locale/pt/LC_MESSAGES/djangojs.po
@@ -0,0 +1,27 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2007-09-15 19:15+0200\n"
+"PO-Revision-Date: 2010-05-12 12:41-0300\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+
+msgid "{count} plural2"
+msgid_plural "{count} plural2s"
+msgstr[0] "{count} plural2"
+msgstr[1] "{count} plural2s"
+
+msgid "{count} plural3"
+msgid_plural "{count} plural3s"
+msgstr[0] "{count} plural3"
+msgstr[1] "{count} plural3s"
diff --git a/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.mo b/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.mo
index 21659a93d3..cb0a8d10db 100644
Binary files a/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.mo and b/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.mo differ
diff --git a/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.po b/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.po
index 4ea193a880..e9eda86192 100644
--- a/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.po
+++ b/tests/view_tests/locale/ru/LC_MESSAGES/djangojs.po
@@ -22,3 +22,16 @@ msgstr "перевод"
 
 msgid "Choose a time"
 msgstr "Выберите время"
+
+
+msgid "{count} plural2"
+msgid_plural "{count} plural2s"
+msgstr[0] ""
+msgstr[1] ""
+msgstr[2] ""
+
+msgid "{count} plural3"
+msgid_plural "{count} plural3s"
+msgstr[0] "{count} plural3 p3"
+msgstr[1] "{count} plural3 p3s"
+msgstr[2] "{count} plural3 p3t"
diff --git a/tests/view_tests/tests/test_i18n.py b/tests/view_tests/tests/test_i18n.py
index 4778b5dd37..bde0ad42d4 100644
--- a/tests/view_tests/tests/test_i18n.py
+++ b/tests/view_tests/tests/test_i18n.py
@@ -314,6 +314,18 @@ class JsI18NTests(SimpleTestCase):
             self.assertContains(response, 'il faut le traduire')
             self.assertNotContains(response, "Untranslated string")
 
+    def test_i18n_fallback_language_plural(self):
+        """
+        The fallback to a language with less plural forms maintains the real
+        language's number of plural forms.
+        """
+        with self.settings(LANGUAGE_CODE='pt'), override('ru'):
+            response = self.client.get('/jsi18n/')
+            self.assertEqual(
+                response.context['catalog']['{count} plural3'],
+                ['{count} plural3', '{count} plural3s', '{count} plural3 p3t']
+            )
+
     def test_i18n_english_variant(self):
         with override('en-gb'):
             response = self.client.get('/jsi18n/')
diff --git a/tests/view_tests/tests/test_i18n_deprecated.py b/tests/view_tests/tests/test_i18n_deprecated.py
index 88ce57f47a..e60a04ad01 100644
--- a/tests/view_tests/tests/test_i18n_deprecated.py
+++ b/tests/view_tests/tests/test_i18n_deprecated.py
@@ -95,6 +95,18 @@ class JsI18NTests(SimpleTestCase):
             self.assertContains(response, 'il faut le traduire')
             self.assertNotContains(response, "Untranslated string")
 
+    def test_i18n_fallback_language_plural(self):
+        """
+        The fallback to a language with less plural forms maintains the real
+        language's number of plural forms.
+        """
+        with self.settings(LANGUAGE_CODE='pt'), override('ru'):
+            response = self.client.get('/jsi18n/')
+            self.assertEqual(
+                response.context['catalog']['{count} plural3'],
+                ['{count} plural3', '{count} plural3s', '{count} plural3 p3t']
+            )
+
     def test_i18n_english_variant(self):
         with override('en-gb'):
             response = self.client.get('/old_jsi18n/')