--- a/compare_locales/checks.py
+++ b/compare_locales/checks.py
@@ -7,16 +7,17 @@ from collections import Counter
 from difflib import SequenceMatcher
 from xml import sax
 try:
     from cStringIO import StringIO
 except ImportError:
     from StringIO import StringIO
 
 from compare_locales.parser import DTDParser, PropertiesEntity
+from compare_locales import plurals
 
 
 class Checker(object):
     '''Abstract class to implement checks per file type.
     '''
     pattern = None
     # if a check uses all reference entities, set this to True
     needs_reference = False
@@ -67,18 +68,22 @@ class PropertiesChecker(Checker):
 
     def check(self, refEnt, l10nEnt):
         '''Test for the different variable formats.
         '''
         refValue, l10nValue = refEnt.val, l10nEnt.val
         refSpecs = None
         # check for PluralForm.jsm stuff, should have the docs in the
         # comment
+        # That also includes intl.properties' pluralRule, so exclude
+        # entities with that key and values with just numbers
         if (refEnt.pre_comment
-                and 'Localization_and_Plurals' in refEnt.pre_comment.all):
+                and 'Localization_and_Plurals' in refEnt.pre_comment.all
+                and refEnt.key != 'pluralRule'
+                and not re.match(r'\d+$', refValue)):
             for msg_tuple in self.check_plural(refValue, l10nValue):
                 yield msg_tuple
             return
         # check for lost escapes
         raw_val = l10nEnt.raw_val
         for m in PropertiesEntity.escape.finditer(raw_val):
             if m.group('single') and \
                m.group('single') not in PropertiesEntity.known_escapes:
@@ -93,16 +98,27 @@ class PropertiesChecker(Checker):
             for t in self.checkPrintf(refSpecs, l10nValue):
                 yield t
             return
 
     def check_plural(self, refValue, l10nValue):
         '''Check for the stringbundle plurals logic.
         The common variable pattern is #1.
         '''
+        if self.locale in plurals.CATEGORIES_BY_LOCALE:
+            expected_forms = len(plurals.CATEGORIES_BY_LOCALE[self.locale])
+            found_forms = l10nValue.count(';') + 1
+            msg = 'expecting {} plurals, found {}'.format(
+                expected_forms,
+                found_forms
+            )
+            if expected_forms > found_forms:
+                yield ('warning', 0, msg, 'plural')
+            if expected_forms < found_forms:
+                yield ('warning', 0, msg, 'plural')
         pats = set(int(m.group(1)) for m in re.finditer('#([0-9]+)',
                                                         refValue))
         if len(pats) == 0:
             return
         lpats = set(int(m.group(1)) for m in re.finditer('#([0-9]+)',
                                                          l10nValue))
         if pats - lpats:
             yield ('warning', 0, 'not all variables used in l10n',

--- a/compare_locales/tests/test_checks.py
+++ b/compare_locales/tests/test_checks.py
@@ -85,16 +85,45 @@ downloadsTitleFiles=#1 file - Downloads;
 # See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
 # #1 number of files
 # example: 111 files - Downloads
 downloadsTitleFiles=#1 file - Downloads;#1 files - #2;#1 #3
 ''',
                    (('error', 0, 'unreplaced variables in l10n', 'plural'),))
 
 
+class TestPluralForms(BaseHelper):
+    file = File('foo.properties', 'foo.properties', locale='en-GB')
+    refContent = '''\
+# LOCALIZATION NOTE (downloadsTitleFiles): Semi-colon list of plural forms.
+# See: http://developer.mozilla.org/en/docs/Localization_and_Plurals
+# #1 number of files
+# example: 111 files - Downloads
+downloadsTitleFiles=#1 file;#1 files
+'''
+
+    def test_matching_forms(self):
+        self._test('''\
+downloadsTitleFiles=#1 fiiilee;#1 fiiilees
+''',
+                   tuple())
+
+    def test_lacking_forms(self):
+        self._test('''\
+downloadsTitleFiles=#1 fiiilee
+''',
+                   (('warning', 0, 'expecting 2 plurals, found 1', 'plural'),))
+
+    def test_excess_forms(self):
+        self._test('''\
+downloadsTitleFiles=#1 fiiilee;#1 fiiilees;#1 fiiilees
+''',
+                   (('warning', 0, 'expecting 2 plurals, found 3', 'plural'),))
+
+
 class TestDTDs(BaseHelper):
     file = File('foo.dtd', 'foo.dtd')
     refContent = '''<!ENTITY foo "This is &apos;good&apos;">
 <!ENTITY width "10ch">
 <!ENTITY style "width: 20ch; height: 280px;">
 <!ENTITY minStyle "min-height: 50em;">
 <!ENTITY ftd "0">
 <!ENTITY formatPercent "This is 100&#037; correct">