diff --git a/source/java/org/alfresco/rest/api/impl/GroupsImpl.java b/source/java/org/alfresco/rest/api/impl/GroupsImpl.java
index d3c3ae06c3..18573089f9 100644
--- a/source/java/org/alfresco/rest/api/impl/GroupsImpl.java
+++ b/source/java/org/alfresco/rest/api/impl/GroupsImpl.java
@@ -623,6 +623,12 @@ public class GroupsImpl implements Groups
             throw new EntityNotFoundException("Group member with id " + groupMember.getId() + " does not exists");
         }
 
+        AuthorityType existingAuthorityType = AuthorityType.getAuthorityType(groupMember.getId());
+        if (existingAuthorityType != authorityType)
+        {
+            throw new IllegalArgumentException("Incorrect group member type, " + existingAuthorityType + " exists with the given id");
+        }
+
         authorityService.addAuthority(groupId, groupMember.getId());
         String authority = authorityService.getName(authorityType, groupMember.getId());
 
@@ -728,7 +734,7 @@ public class GroupsImpl implements Groups
             throw new EntityNotFoundException(groupId);
         }
     }
-
+    
     private void validateGroup(Group group, boolean isUpdate)
     {
         if (group == null)
diff --git a/source/test-java/org/alfresco/rest/api/tests/GroupsTest.java b/source/test-java/org/alfresco/rest/api/tests/GroupsTest.java
index 8dfa6d06bc..93824e05ef 100644
--- a/source/test-java/org/alfresco/rest/api/tests/GroupsTest.java
+++ b/source/test-java/org/alfresco/rest/api/tests/GroupsTest.java
@@ -956,14 +956,14 @@ public class GroupsTest extends AbstractSingleNetworkSiteTest
                 people.create(personAlice);
             }
 
+            GroupMember personMember = new GroupMember();
+            personMember.setId(personAlice.getId());
+            personMember.setMemberType(MEMBER_TYPE_PERSON);
+
             // +ve tests
             // Create a group membership (for a existing person and a sub-group)
             // within a group groupId
             {
-                GroupMember personMember = new GroupMember();
-                personMember.setId(personAlice.getId());
-                personMember.setMemberType(MEMBER_TYPE_PERSON);
-
                 // Add person as groupB member
                 groupsProxy.createGroupMember(groupB.getId(), personMember, HttpServletResponse.SC_CREATED);
                 // Add group as groupB sub-group
@@ -986,6 +986,13 @@ public class GroupsTest extends AbstractSingleNetworkSiteTest
                 assertFalse("Group was expected to be sub-group.", subGroup.getIsRoot());
             }
 
+            // -ve tests
+            // Id clashes with an existing group member
+            {
+                //Add a group member that has been already added
+                groupsProxy.createGroupMember(groupB.getId(), groupMemberA, HttpServletResponse.SC_CONFLICT);
+            }
+
             // Person or group with given id does not exists
             {
                 GroupMember invalidIdGroupMember = new GroupMember();
@@ -1014,12 +1021,40 @@ public class GroupsTest extends AbstractSingleNetworkSiteTest
                 groupsProxy.createGroupMember(groupA.getId(), invalidGroupMember, HttpServletResponse.SC_BAD_REQUEST);
             }
 
-            // -ve tests
-            // Add group with non-admin user
+            // Validation tests
+            {
+                // Add group as groupB sub-group with member id null
+                personMember.setId(null);
+                groupsProxy.createGroupMember(groupB.getId(), personMember, HttpServletResponse.SC_BAD_REQUEST);
+                // Add group as groupB sub-group with member display name null
+                personMember.setDisplayName(null);
+                groupsProxy.createGroupMember(groupB.getId(), personMember, HttpServletResponse.SC_BAD_REQUEST);
+                // Add group as groupB sub-group with member type null
+                personMember.setMemberType(null);
+                groupsProxy.createGroupMember(groupB.getId(), personMember, HttpServletResponse.SC_BAD_REQUEST);
+            }
+
+            // Add group member with a different type from the existing one
+            {
+                // Add person as groupB member with member type GROUP
+                personMember.setMemberType(MEMBER_TYPE_GROUP);
+                groupsProxy.createGroupMember(groupB.getId(), personMember, HttpServletResponse.SC_BAD_REQUEST);
+                // Add group as groupB sub-group with member type PERSON
+                groupMemberA.setMemberType(MEMBER_TYPE_PERSON);
+                groupsProxy.createGroupMember(groupB.getId(), groupMemberA, HttpServletResponse.SC_BAD_REQUEST);
+            }
+
+            // User does not have admin permission to create a group membership
             {
                 setRequestContext(user1);
-                groupsProxy.createGroupMember(groupA.getId(), groupMemberA, HttpServletResponse.SC_FORBIDDEN);
+                groupsProxy.createGroupMember(groupB.getId(), groupMemberB, HttpServletResponse.SC_FORBIDDEN);
             }
+            //Authentication failed
+            {
+                setRequestContext(networkOne.getId(), GUID.generate(), "password");
+                groupsProxy.createGroupMember(groupB.getId(), groupMemberB, HttpServletResponse.SC_UNAUTHORIZED);
+            }
+
         }
         finally
         {