diff --git a/SeedDMS_Core/Core/inc.ClassUser.php b/SeedDMS_Core/Core/inc.ClassUser.php
index a8900ccf4..3af9c67b7 100644
--- a/SeedDMS_Core/Core/inc.ClassUser.php
+++ b/SeedDMS_Core/Core/inc.ClassUser.php
@@ -975,7 +975,7 @@ class SeedDMS_Core_User { /* {{{ */
 						if($version = $doc->getContentByVersion($ri['version'])) {
 							$ret = $version->addIndReviewer($newuser, $user);
 							/* returns -3 if the user is already a reviewer */ 
-							if($ret != 0 && $ret != -3) {
+							if($ret === false || ($ret < 0 && $ret != -3)) {
 								$db->rollbackTransaction();
 								return false;
 							}
@@ -1004,7 +1004,7 @@ class SeedDMS_Core_User { /* {{{ */
 						if($version = $doc->getContentByVersion($ai['version'])) {
 							$ret = $version->addIndReviewer($newuser, $user);
 							/* returns -3 if the user is already a reviewer */ 
-							if($ret != 0 && $ret != -3) {
+							if($ret === false || ($ret < 0 && $ret != -3)) {
 								$db->rollbackTransaction();
 								return false;
 							}
@@ -1033,7 +1033,7 @@ class SeedDMS_Core_User { /* {{{ */
 						if($version = $doc->getContentByVersion($ri['version'])) {
 							$ret = $version->addIndRecipient($newuser, $user);
 							/* returns -3 if the user is already a recipient */ 
-							if($ret != 0 && $ret != -3) {
+							if($ret === false || ($ret < 0 && $ret != -3)) {
 								$db->rollbackTransaction();
 								return false;
 							}
@@ -1062,7 +1062,7 @@ class SeedDMS_Core_User { /* {{{ */
 						if($version = $doc->getContentByVersion($ri['version'])) {
 							$ret = $version->addIndRevisor($newuser, $user);
 							/* returns -3 if the user is already a revisor */ 
-							if($ret != 0 && $ret != -3) {
+							if($ret === false || ($ret < 0 && $ret != -3)) {
 								$db->rollbackTransaction();
 								return false;
 							}