diff --git a/src/emu/bus/pce/pce_slot.c b/src/emu/bus/pce/pce_slot.c
index aaf4ab63257..611525a6a53 100644
--- a/src/emu/bus/pce/pce_slot.c
+++ b/src/emu/bus/pce/pce_slot.c
@@ -309,11 +309,11 @@ int pce_cart_slot_device::get_cart_type(UINT8 *ROM, UINT32 len)
 		type = PCE_POPULOUS;
 
 	// Check for CD system card v3 which adds on-cart RAM to the system
-	if (!memcmp(ROM + 0x3FFB6, "PC Engine CD-ROM SYSTEM", 23))
+	if (len >= 0x3ffb6 + 23 && !memcmp(ROM + 0x3ffb6, "PC Engine CD-ROM SYSTEM", 23))
 	{
 		/* Check if 192KB additional system card ram should be used */
-		if(!memcmp(ROM + 0x29D1, "VER. 3.", 7))         { type = PCE_CDSYS3J; } // JP version
-		else if(!memcmp(ROM + 0x29C4, "VER. 3.", 7 ))   { type = PCE_CDSYS3U; } // US version
+		if (!memcmp(ROM + 0x29d1, "VER. 3.", 7))         { type = PCE_CDSYS3J; } // JP version
+		else if (!memcmp(ROM + 0x29c4, "VER. 3.", 7 ))   { type = PCE_CDSYS3U; } // US version
 	}
 
 	return type;