diff --git a/src/emu/bus/coleco/std.c b/src/emu/bus/coleco/std.c
index 09b5de59059..b8d4ecea207 100644
--- a/src/emu/bus/coleco/std.c
+++ b/src/emu/bus/coleco/std.c
@@ -53,7 +53,10 @@ UINT8 colecovision_standard_cartridge_device::bd_r(address_space &space, offs_t
 {
 	if (!_8000 || !_a000 || !_c000 || !_e000)
 	{
-		data = m_rom[offset & m_rom.mask()];
+		if (offset < m_rom.bytes())
+			data = m_rom[offset];
+		else
+			data = 0xff;
 	}
 
 	return data;