diff --git a/lib/github/ldap.rb b/lib/github/ldap.rb
index ebdfddc..0545247 100644
--- a/lib/github/ldap.rb
+++ b/lib/github/ldap.rb
@@ -19,7 +19,7 @@ class Ldap
 
     # Internal: The capability required to use ActiveDirectory features.
     # See: http://msdn.microsoft.com/en-us/library/cc223359.aspx.
-    ACTIVE_DIRECTORY_V61_R2_OID = "1.2.840.113556.1.4.2080".freeze
+    ACTIVE_DIRECTORY_V51_OID = "1.2.840.113556.1.4.1670".freeze
 
     # Utility method to get the last operation result with a human friendly message.
     #
@@ -313,7 +313,7 @@ def configure_member_search_strategy(strategy = nil)
     #
     # Returns true if the host is an ActiveDirectory server, false otherwise.
     def active_directory_capability?
-      capabilities[:supportedcapabilities].include?(ACTIVE_DIRECTORY_V61_R2_OID)
+      capabilities[:supportedcapabilities].include?(ACTIVE_DIRECTORY_V51_OID)
     end
     private :active_directory_capability?
   end
diff --git a/test/ldap_test.rb b/test/ldap_test.rb
index 48511d8..c7b24c4 100644
--- a/test/ldap_test.rb
+++ b/test/ldap_test.rb
@@ -80,7 +80,7 @@ def test_search_strategy_defaults
 
   def test_search_strategy_detects_active_directory
     caps = Net::LDAP::Entry.new
-    caps[:supportedcapabilities] = [GitHub::Ldap::ACTIVE_DIRECTORY_V61_R2_OID]
+    caps[:supportedcapabilities] = [GitHub::Ldap::ACTIVE_DIRECTORY_V51_OID]
 
     @ldap.stub :capabilities, caps do
       @ldap.configure_search_strategy :detect