diff --git a/src/smq/snmp/snmp.go b/src/smq/snmp/snmp.go
index c4ea63d..51b8fb6 100644
--- a/src/smq/snmp/snmp.go
+++ b/src/smq/snmp/snmp.go
@@ -56,6 +56,9 @@ func calculateDifference(key string, newValue string) (string, error) {
       Timestamp: currentTime,
       Value: newValue,
     }
+    if diffValuePerSecond < 0 {
+      return "", fmt.Errorf("negative difference value: %d", diffValuePerSecond)
+    }
     return strconv.Itoa(diffValuePerSecond), nil
   } else {
     log.Printf("create lvv for %s", key)
@@ -122,8 +125,6 @@ func Start() {
                 if err != nil {
                   log.Printf("Error when building difference: %v", err)
                   convertedValue = "-1"
-                } else if diff < 0 {
-                  convertedValue = "-2"
                 } else {
                   convertedValue = diff 
                 }