diff --git a/internal/services/iothub/iothub_endpoint_storage_container_resource.go b/internal/services/iothub/iothub_endpoint_storage_container_resource.go
index 19e9306177068..cb6b222c4e450 100644
--- a/internal/services/iothub/iothub_endpoint_storage_container_resource.go
+++ b/internal/services/iothub/iothub_endpoint_storage_container_resource.go
@@ -65,7 +65,7 @@ func resourceIotHubEndpointStorageContainer() *pluginsdk.Resource {
 			"file_name_format": {
 				Type:     pluginsdk.TypeString,
 				Optional: true,
-				Default:  false,
+				ValidateFunc: iothubValidate.FileNameFormat,
 			},
 
 			"batch_frequency_in_seconds": {