diff --git a/src/emu/cpu/psx/psx.c b/src/emu/cpu/psx/psx.c
index 13b9d7c3f7a..70de7d11a41 100644
--- a/src/emu/cpu/psx/psx.c
+++ b/src/emu/cpu/psx/psx.c
@@ -3280,6 +3280,7 @@ static MACHINE_CONFIG_FRAGMENT( psx )
 	MCFG_PSX_SIO_IRQ_HANDLER(DEVWRITELINE("irq", psxirq_device, intin8))
 
 	MCFG_RAM_ADD("ram")
+	MCFG_RAM_DEFAULT_VALUE(0x00)
 MACHINE_CONFIG_END
 
 //-------------------------------------------------