diff --git a/src/emu/memory.c b/src/emu/memory.c
index fc4b79971d0..3224e9d11d2 100644
--- a/src/emu/memory.c
+++ b/src/emu/memory.c
@@ -1811,7 +1811,7 @@ void address_space::prepare_map()
 	m_map.reset(global_alloc(address_map(m_device, m_spacenum)));
 
 	// merge in the submaps
-	m_map->uplift_submaps(machine(), m_device, *m_device.owner(), endianness());
+	m_map->uplift_submaps(machine(), m_device, m_device.owner() ? *m_device.owner() : m_device, endianness());
 
 	// extract global parameters specified by the map
 	m_unmap = (m_map->m_unmapval == 0) ? 0 : ~0;