diff --git a/resource_compute_forwarding_rule.go b/resource_compute_forwarding_rule.go
index 99684560..529588fd 100644
--- a/resource_compute_forwarding_rule.go
+++ b/resource_compute_forwarding_rule.go
@@ -90,6 +90,7 @@ func resourceComputeForwardingRule() *schema.Resource {
 				Optional: true,
 				ForceNew: true,
 				Set:      schema.HashString,
+				MaxItems: 5,
 			},
 
 			"project": &schema.Schema{