diff --git a/engine/statmetrics.go b/engine/statmetrics.go
index ee2aed256..6d21af3fd 100644
--- a/engine/statmetrics.go
+++ b/engine/statmetrics.go
@@ -556,6 +556,8 @@ func (acc *StatACC) AddEvent(evID string, ev utils.DataProvider) (err error) {
 		return
 	} else if cost, err = utils.IfaceAsFloat64(val); err != nil {
 		return
+	} else if cost < 0 {
+		return utils.ErrPrefix(utils.ErrNegative, utils.Cost)
 	}
 	acc.Sum += cost
 	if val, has := acc.Events[evID]; !has {
@@ -686,6 +688,8 @@ func (tcc *StatTCC) AddEvent(evID string, ev utils.DataProvider) (err error) {
 		return
 	} else if cost, err = utils.IfaceAsFloat64(val); err != nil {
 		return
+	} else if cost < 0 {
+		return utils.ErrPrefix(utils.ErrNegative, utils.Cost)
 	}
 	tcc.Sum += cost
 	if val, has := tcc.Events[evID]; !has {
diff --git a/engine/statmetrics_test.go b/engine/statmetrics_test.go
index 7f5b3cf8e..86c647c23 100644
--- a/engine/statmetrics_test.go
+++ b/engine/statmetrics_test.go
@@ -1052,6 +1052,12 @@ func TestACCGetStringValue(t *testing.T) {
 	if strVal := acc.GetStringValue(config.CgrConfig().GeneralCfg().RoundingDecimals); strVal != utils.NotAvailable {
 		t.Errorf("wrong acc value: %s", strVal)
 	}
+	expErr := "NEGATIVE:Cost"
+	if err := acc.AddEvent(ev5.ID, utils.MapStorage{utils.MetaReq: utils.MapStorage{
+		utils.Cost: -1,
+	}}); err == nil || err.Error() != expErr {
+		t.Errorf("Expected error: %s received %v", expErr, err)
+	}
 }
 
 func TestACCGetStringValue2(t *testing.T) {
@@ -1322,6 +1328,13 @@ func TestTCCGetStringValue(t *testing.T) {
 	if strVal := tcc.GetStringValue(config.CgrConfig().GeneralCfg().RoundingDecimals); strVal != utils.NotAvailable {
 		t.Errorf("wrong tcc value: %s", strVal)
 	}
+
+	expErr := "NEGATIVE:Cost"
+	if err := tcc.AddEvent(ev5.ID, utils.MapStorage{utils.MetaReq: utils.MapStorage{
+		utils.Cost: -1,
+	}}); err == nil || err.Error() != expErr {
+		t.Errorf("Expected error: %s received %v", expErr, err)
+	}
 }
 
 func TestTCCGetStringValue2(t *testing.T) {
diff --git a/packages/debian/changelog b/packages/debian/changelog
index a03f65336..4fa6ccc57 100644
--- a/packages/debian/changelog
+++ b/packages/debian/changelog
@@ -162,6 +162,7 @@ cgrates (0.11.0~dev) UNRELEASED; urgency=medium
   * [ERs] Added *opts.*partial to control if the event is partial or not
   * [AttributeS] Added any_context config to control the matching attributes
   * [DispatcherS] Added any_subsyste config to control the matching dispatchers
+  * [StatS] AverageCallCost and TotalCallCost now returns error for negative Cost field
 
  -- DanB <danb@cgrates.org>  Wed, 19 Feb 2020 13:25:52 +0200
 
diff --git a/utils/errors.go b/utils/errors.go
index aef7d2047..d1716bc9b 100644
--- a/utils/errors.go
+++ b/utils/errors.go
@@ -75,6 +75,7 @@ var (
 	ErrMaxConcurentRPCExceededNoCaps = errors.New("max concurent rpc exceeded") // on internal we return this error for concureq
 	ErrMaxConcurentRPCExceeded       = errors.New("MAX_CONCURENT_RPC_EXCEEDED") // but the codec will rewrite it with this one to be sure that we corectly dealocate the request
 	ErrMaxIterationsReached          = errors.New("maximum iterations reached")
+	ErrNegative                      = errors.New("NEGATIVE")
 
 	ErrMap = map[string]error{
 		ErrNoMoreData.Error():              ErrNoMoreData,