diff --git a/pkg/services/alerting/eval_handler.go b/pkg/services/alerting/eval_handler.go
index ed77877e34d..fd6d2687a33 100644
--- a/pkg/services/alerting/eval_handler.go
+++ b/pkg/services/alerting/eval_handler.go
@@ -52,12 +52,15 @@ func (e *DefaultEvalHandler) Eval(context *EvalContext) {
 		// calculating Firing based on operator
 		if cr.Operator == "or" {
 			firing = firing || cr.Firing
-			noDataFound = noDataFound || cr.NoDataFound
 		} else {
 			firing = firing && cr.Firing
-			noDataFound = noDataFound && cr.NoDataFound
 		}
 
+		// We cannot evaluate the expression when one or more conditions are missing data
+		// and so noDataFound should be true if at least one condition returns no data,
+		// irrespective of the operator.
+		noDataFound = noDataFound || cr.NoDataFound
+
 		if i > 0 {
 			conditionEvals = "[" + conditionEvals + " " + strings.ToUpper(cr.Operator) + " " + strconv.FormatBool(cr.Firing) + "]"
 		} else {
diff --git a/pkg/services/alerting/eval_handler_test.go b/pkg/services/alerting/eval_handler_test.go
index 271d51c385d..12ac6c84a20 100644
--- a/pkg/services/alerting/eval_handler_test.go
+++ b/pkg/services/alerting/eval_handler_test.go
@@ -182,7 +182,7 @@ func TestAlertingEvaluationHandler(t *testing.T) {
 			So(context.NoDataFound, ShouldBeTrue)
 		})
 
-		Convey("Should not return no data if at least one condition has no data and using AND", func() {
+		Convey("Should return no data if at least one condition has no data and using AND", func() {
 			context := NewEvalContext(context.TODO(), &Rule{
 				Conditions: []Condition{
 					&conditionStub{operator: "and", noData: true},
@@ -191,7 +191,7 @@ func TestAlertingEvaluationHandler(t *testing.T) {
 			}, &validations.OSSPluginRequestValidator{})
 
 			handler.Eval(context)
-			So(context.NoDataFound, ShouldBeFalse)
+			So(context.NoDataFound, ShouldBeTrue)
 		})
 
 		Convey("Should return no data if at least one condition has no data and using OR", func() {