From b93a07dcfa97e4bc0ccdfde6b19211de864a98f5 Mon Sep 17 00:00:00 2001
From: Christian Speckner <christian.speckner@mayflower.de>
Date: Thu, 2 Apr 2020 21:14:49 +0200
Subject: [PATCH] 3E: fix invalid access on write to ROM.

---
 src/emucore/Cart3E.cxx | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/emucore/Cart3E.cxx b/src/emucore/Cart3E.cxx
index 15084b53e..3f2b1263f 100644
--- a/src/emucore/Cart3E.cxx
+++ b/src/emucore/Cart3E.cxx
@@ -115,6 +115,9 @@ bool Cartridge3E::poke(uInt16 address, uInt8 value)
   }
   else
   {
+    if (myCurrentBank < 256)
+      return false;
+
     if(address & 0x0400)
     {
       pokeRAM(myRAM[(address & 0x03FF) + ((myCurrentBank - 256) << 10)], pokeAddress, value);