diff --git a/src/mame/machine/psion_pack.cpp b/src/mame/machine/psion_pack.cpp
index a773f7114e5..070e477d0c8 100644
--- a/src/mame/machine/psion_pack.cpp
+++ b/src/mame/machine/psion_pack.cpp
@@ -94,7 +94,7 @@ void datapack_device::device_start()
 
 void datapack_device::device_config_complete()
 {
-	m_formatlist.push_back(std::make_unique<image_device_format>("opk", "Psion Datapack image", "opk", datapack_option_spec));
+	add_format("opk", "Psion Datapack image", "opk", datapack_option_spec);
 
 	// set brief and instance name
 	update_names();