diff --git a/src/vid_et4000w32.c b/src/vid_et4000w32.c
index 8b5e5f3..680e937 100644
--- a/src/vid_et4000w32.c
+++ b/src/vid_et4000w32.c
@@ -379,8 +379,11 @@ void et4000w32p_mmu_write(uint32_t addr, uint8_t val, void *p)
                 }
                 else
                 {
-                        svga->vram[(addr & 0x1fff) + et4000->mmu.base[bank]] = val;
-                        svga->changedvram[((addr & 0x1fff) + et4000->mmu.base[bank]) >> 12] = changeframecount;
+                        if ((addr&0x1fff) + et4000->mmu.base[bank] < svga->vram_limit)
+                        {
+                                svga->vram[(addr & 0x1fff) + et4000->mmu.base[bank]] = val;
+                                svga->changedvram[((addr & 0x1fff) + et4000->mmu.base[bank]) >> 12] = changeframecount;
+                        }
                 }
                 break;
                 case 0x6000:
@@ -483,6 +486,8 @@ uint8_t et4000w32p_mmu_read(uint32_t addr, void *p)
                         /*???*/
                         return temp;
                 }
+                if ((addr&0x1fff) + et4000->mmu.base[bank] >= svga->vram_limit)
+                        return 0xff;
                 return svga->vram[(addr&0x1fff) + et4000->mmu.base[bank]];
                 
                 case 0x6000: