diff --git a/glaurung.sav b/glaurung.sav
new file mode 100644
index 0000000..5cb2fa0
Binary files /dev/null and b/glaurung.sav differ
diff --git a/z80.cpp b/z80.cpp
index 35b8d11..750017c 100644
--- a/z80.cpp
+++ b/z80.cpp
@@ -10,7 +10,7 @@ namespace z80
     static uint8_t memtouched[65536];
     static uint32_t t = 0;
     static uint16_t current_opcode_address = 0;
-    bool options[Z80_NUM_OPTIONS] = { true };
+    bool options[Z80_NUM_OPTIONS] = { true, false };
 
     int (*in_ports[256])(int);
     void (*out_ports[256])(int, int);
@@ -666,7 +666,12 @@ namespace z80
         } else if (im==2) {
             const uint16_t address = (rI<<8) | 0xFE;
             rPC = READ_MEM_16(address);
+        } else if (im==0) {
+            printf("Interrupt mode 0!\n");
+            z80debug::stop();
+            return;
         }
+        if (options[Z80_OPTION_BREAK_ON_INTERRUPT]) z80debug::stop();
     }
 
     void RST(uint8_t vec)
diff --git a/z80.h b/z80.h
index 053128e..ee9e72c 100644
--- a/z80.h
+++ b/z80.h
@@ -10,7 +10,8 @@ namespace z80
     #define MEMTAG_DATA     3
 
     #define Z80_OPTION_STOP_ON_INVALID  0
-    #define Z80_NUM_OPTIONS 1
+    #define Z80_OPTION_BREAK_ON_INTERRUPT 1
+    #define Z80_NUM_OPTIONS 2
     
     void reset(uint8_t* mem);
     void connect_port(int num, int (*in_ptr)(int), void (*out_ptr)(int,int));
diff --git a/z80debug.cpp b/z80debug.cpp
index 69fc888..ac53704 100644
--- a/z80debug.cpp
+++ b/z80debug.cpp
@@ -623,6 +623,7 @@ namespace z80debug
         } else if (strcmp(cmd, "b")==0 || strcmp(cmd, "break")==0) {
             getcmd();
             if (cmd[0] == 0) { breakpoints[z80::getPC()]=1; return; }
+            if (cmd[0] == 'i') { z80::setOption(Z80_OPTION_BREAK_ON_INTERRUPT, !z80::getOption(Z80_OPTION_BREAK_ON_INTERRUPT)); return; }
             int address = getnum(cmd);
             if (address<0 || address>65536) { sendToConsoleLog("Illegal break address"); return; }
             getcmd();