diff --git a/model/event.go b/model/event.go
index bad1ce4..ddc5ab2 100644
--- a/model/event.go
+++ b/model/event.go
@@ -96,8 +96,8 @@ type EventRef struct {
 	// +kubebuilder:validation:Required
 	TriggerEventRef string `json:"triggerEventRef" validate:"required"`
 	// Reference to the unique name of a 'consumed' event definition
-	// +kubebuilder:validation:Required
-	ResultEventRef string `json:"resultEventRef" validate:"required"`
+	// +optional
+	ResultEventRef string `json:"resultEventRef"`
 	// Maximum amount of time (ISO 8601 format) to wait for the result event. If not defined it be set to the
 	// actionExecutionTimeout
 	// +optional
diff --git a/model/event_validator_test.go b/model/event_validator_test.go
index 80340b0..89566e8 100644
--- a/model/event_validator_test.go
+++ b/model/event_validator_test.go
@@ -175,11 +175,9 @@ func TestEventRefStructLevelValidation(t *testing.T) {
 			Model: func() Workflow {
 				model := baseWorkflow.DeepCopy()
 				model.States[0].OperationState.Actions[0].EventRef.TriggerEventRef = ""
-				model.States[0].OperationState.Actions[0].EventRef.ResultEventRef = ""
 				return *model
 			},
-			Err: `workflow.states[0].actions[0].eventRef.triggerEventRef is required
-workflow.states[0].actions[0].eventRef.resultEventRef is required`,
+			Err: `workflow.states[0].actions[0].eventRef.triggerEventRef is required`,
 		},
 		{
 			Desp: "exists",