diff --git a/attributemap/deprecatedSchacNS.php b/attributemap/deprecatedSchacNS.php
index f4771632423129cbc2bceb00be52dd0a56030d38..5f90e03ab7a95cf2720c3706674cb80a7d71840e 100644
--- a/attributemap/deprecatedSchacNS.php
+++ b/attributemap/deprecatedSchacNS.php
@@ -3,8 +3,13 @@
  * This file provides translations from the schac namespace to the old, deprecated namespace provided by TERENA.
  */
 
-define('SCHAC_OLD_NS', 'urn:mace:terena.org:attribute-def:');
-define('SCHAC_NEW_NS', 'urn:schac:attribute-def:');
+if (!defined('SCHAC_OLD_NS')) {
+    define('SCHAC_OLD_NS', 'urn:mace:terena.org:attribute-def:');
+}
+
+if (!defined('SCHAC_NEW_NS')) {
+    define('SCHAC_NEW_NS', 'urn:schac:attribute-def:');
+}
 
 $attributemap = array(
     SCHAC_NEW_NS.'schacCountryOfCitizenship' => SCHAC_OLD_NS.'schacCountryOfCitizenship',
diff --git a/attributemap/newSchacNS.php b/attributemap/newSchacNS.php
index 80f621c087eab8d354d33488b0460d83632674f0..8b3d2a75685f392c9c73c56431b2e31c947d6c78 100644
--- a/attributemap/newSchacNS.php
+++ b/attributemap/newSchacNS.php
@@ -3,8 +3,13 @@
  * This file provides translations from the deprecated schac namespace provided by TERENA, to the new namespace.
  */
 
-define('SCHAC_OLD_NS', 'urn:mace:terena.org:attribute-def:');
-define('SCHAC_NEW_NS', 'urn:schac:attribute-def:');
+if (!defined('SCHAC_OLD_NS')) {
+    define('SCHAC_OLD_NS', 'urn:mace:terena.org:attribute-def:');
+}
+
+if (!defined('SCHAC_NEW_NS')) {
+    define('SCHAC_NEW_NS', 'urn:schac:attribute-def:');
+}
 
 $attributemap = array(
     SCHAC_OLD_NS.'schacCountryOfCitizenship' => SCHAC_NEW_NS.'schacCountryOfCitizenship',