diff --git a/lib/net/ldap/filter.rb b/lib/net/ldap/filter.rb
index 6f064488..94652327 100644
--- a/lib/net/ldap/filter.rb
+++ b/lib/net/ldap/filter.rb
@@ -755,7 +755,7 @@ def parse_paren_expression(scanner)
     # This parses a given expression inside of parentheses.
     def parse_filter_branch(scanner)
       scanner.scan(/\s*/)
-      if token = scanner.scan(/[-\w:.]*[\w]/)
+      if token = scanner.scan(/[-\w:.;]*[\w]/)
         scanner.scan(/\s*/)
         if op = scanner.scan(/<=|>=|!=|:=|=/)
           scanner.scan(/\s*/)
diff --git a/test/test_filter_parser.rb b/test/test_filter_parser.rb
index 6f1ca48b..82fb27d3 100644
--- a/test/test_filter_parser.rb
+++ b/test/test_filter_parser.rb
@@ -21,4 +21,8 @@ def test_slash
   def test_colons
     assert_kind_of Net::LDAP::Filter, Net::LDAP::Filter::FilterParser.parse("(ismemberof=cn=edu:berkeley:app:calmessages:deans,ou=campus groups,dc=berkeley,dc=edu)")
   end
+
+  def test_attr_tag
+    assert_kind_of Net::LDAP::Filter, Net::LDAP::Filter::FilterParser.parse("(mail;primary=jane@example.org)")
+  end
 end