diff --git a/src/devices/bus/pofo/rom.cpp b/src/devices/bus/pofo/rom.cpp
index ac336eb0b77..2e49c3df8dd 100644
--- a/src/devices/bus/pofo/rom.cpp
+++ b/src/devices/bus/pofo/rom.cpp
@@ -48,5 +48,5 @@ void portfolio_rom_card_device::device_start()
 
 uint8_t portfolio_rom_card_device::nrdi_r(offs_t offset)
 {
-	return m_rom[offset];
+	return (m_rom) ? m_rom[offset] : 0xff;
 }