diff --git a/src/smq/snmp/snmp.go b/src/smq/snmp/snmp.go
index e882687..2b60eb2 100644
--- a/src/smq/snmp/snmp.go
+++ b/src/smq/snmp/snmp.go
@@ -114,15 +114,15 @@ func Start() {
                 convertedValue = fmt.Sprintf("%d", gosnmp.ToBigInt(variable.Value))
               }
 
-              diffValue := "-"
               if oidTopic.Diff == "true" {
                 log.Println("Calculate difference to last value")
                 key := endpoint.Endpoint + ":" + oidTopic.OID
                 diff, err := calculateDifference(key, convertedValue)
                 if err != nil {
                   log.Printf("Error when building difference: %v", err)
+                  convertedValue = "-1"
                 } else {
-                  diffValue = diff 
+                  convertedValue = diff 
                 }
               }
 
@@ -131,7 +131,6 @@ func Start() {
                 Label: oidTopic.Label,
                 Variable: oidTopic.OID,
                 Value: convertedValue,
-                DiffValue: diffValue,
               }
               message.Variables[oidTopic.Label] = v