diff --git a/builtin/providers/google/resource_compute_instance_group.go b/builtin/providers/google/resource_compute_instance_group.go
index f0b905bf9..284fc1631 100644
--- a/builtin/providers/google/resource_compute_instance_group.go
+++ b/builtin/providers/google/resource_compute_instance_group.go
@@ -225,7 +225,7 @@ func resourceComputeInstanceGroupUpdate(d *schema.ResourceData, meta interface{}
 			return fmt.Errorf("Error invalid instance URLs: %v", from)
 		}
 		if !validInstanceURLs(to) {
-			return fmt.Errorf("Error invalid instance URLs: %v", from)
+			return fmt.Errorf("Error invalid instance URLs: %v", to)
 		}
 
 		add, remove := calcAddRemove(from, to)