diff --git a/src/386.c b/src/386.c
index 8a03cc4..6b81d79 100644
--- a/src/386.c
+++ b/src/386.c
@@ -10,6 +10,7 @@
 #include "fdc.h"
 #include "pic.h"
 #include "timer.h"
+#include "nmi.h"
 
 #include "386_common.h"
 
@@ -319,7 +320,7 @@ dontprint=0;
                                 loadcs(readmemw(0,addr+2));
                         }
                 }
-                else if (nmi && nmi_enable)
+                else if (nmi && nmi_enable && nmi_mask)
                 {
                         cpu_state.oldpc = cpu_state.pc;
                         oldcs = CS;
diff --git a/src/model.c b/src/model.c
index 5f6bd68..d26d293 100644
--- a/src/model.c
+++ b/src/model.c
@@ -317,6 +317,7 @@ void at_init()
         nvr_init();
         pic2_init();
         device_add(&gameport_device);
+        nmi_mask = 0;
 }
 
 void ibm_at_init()
diff --git a/src/nvr.c b/src/nvr.c
index 9258eea..e4934e0 100644
--- a/src/nvr.c
+++ b/src/nvr.c
@@ -7,6 +7,7 @@
 #include "rtc.h"
 #include "paths.h"
 #include "config.h"
+#include "nmi.h"
 
 int oldromset;
 int nvrmask=63;
@@ -176,7 +177,11 @@ void writenvr(uint16_t addr, uint8_t val, void *priv)
                         }
                 }
         }
-        else        nvraddr=val&nvrmask;
+        else
+        {
+                nvraddr=val&nvrmask;
+                nmi_mask = ~val & 0x80;
+        }
 }
 
 uint8_t readnvr(uint16_t addr, void *priv)
diff --git a/src/scat.c b/src/scat.c
index 2a27a04..14a4406 100644
--- a/src/scat.c
+++ b/src/scat.c
@@ -5,6 +5,7 @@
 #include "mem.h"
 #include "scat.h"
 #include "x86.h"
+#include "nmi.h"
 
 static uint8_t scat_regs[256];
 static int scat_index;
@@ -395,7 +396,7 @@ uint8_t scat_read(uint16_t port, void *priv)
                 switch (scat_index)
                 {
                         case SCAT_MISCELLANEOUS_STATUS:
-                        val = (scat_regs[scat_index] & 0xbf) | ((mem_a20_key & 2) << 5);
+                        val = (scat_regs[scat_index] & 0x3f) | (~nmi_mask & 0x80) | ((mem_a20_key & 2) << 5);
                         break;
                         case SCAT_DRAM_CONFIGURATION:
                         val = (scat_regs[scat_index] & 0x8f) | (cpu_waitstates == 1 ? 0 : 0x10);