diff --git a/api/src/com/cloud/api/commands/DisassociateIPAddrCmd.java b/api/src/com/cloud/api/commands/DisassociateIPAddrCmd.java
index 0714fecbbcc..f092f9953a0 100644
--- a/api/src/com/cloud/api/commands/DisassociateIPAddrCmd.java
+++ b/api/src/com/cloud/api/commands/DisassociateIPAddrCmd.java
@@ -30,6 +30,7 @@ import com.cloud.async.AsyncJob;
 import com.cloud.event.EventTypes;
 import com.cloud.exception.InvalidParameterValueException;
 import com.cloud.network.IpAddress;
+import com.cloud.user.Account;
 import com.cloud.user.UserContext;
 
 @Implementation(description="Disassociates an ip address from the account.", responseObject=SuccessResponse.class)
@@ -96,6 +97,10 @@ public class DisassociateIPAddrCmd extends BaseAsyncCmd {
             }
             ownerId = ip.getAccountId();
         }
+        
+        if (ownerId == null) {
+            return Account.ACCOUNT_ID_SYSTEM;
+        }
         return ownerId;
     }
     
diff --git a/server/src/com/cloud/network/NetworkManagerImpl.java b/server/src/com/cloud/network/NetworkManagerImpl.java
index be9bb10c87c..9836980c1ba 100755
--- a/server/src/com/cloud/network/NetworkManagerImpl.java
+++ b/server/src/com/cloud/network/NetworkManagerImpl.java
@@ -1588,8 +1588,10 @@ public class NetworkManagerImpl implements NetworkManager, NetworkService, Manag
         if (ipVO.getAllocatedToAccountId() != null) {
             _accountMgr.checkAccess(caller, null, ipVO);
         }
+        
+        Network associatedNetwork = getNetwork(ipVO.getAssociatedWithNetworkId());
 
-        if (ipVO.isSourceNat()) {
+        if (isServiceSupportedByNetworkOffering(associatedNetwork.getNetworkOfferingId(), Service.SourceNat)) {
             throw new IllegalArgumentException("ip address is used for source nat purposes and can not be disassociated.");
         }