diff --git a/core/cart_hw/sms_cart.c b/core/cart_hw/sms_cart.c
index c4aba91..47ebfec 100644
--- a/core/cart_hw/sms_cart.c
+++ b/core/cart_hw/sms_cart.c
@@ -255,7 +255,8 @@ static const rominfo_t game_list[] =
   {0x41C948BF, 0, 0, SYSTEM_SPORTSPAD,   MAPPER_SEGA,   SYSTEM_SMS2,        REGION_USA}, /* Sports Pad Soccer */
 
   /* games requiring homemade multitap */
-  {0xFAB6F52F, 0, 0, SYSTEM_MS4PLAY,     MAPPER_NONE,   SYSTEM_SMS2,        REGION_USA}, /* BOom */
+  {0xFAB6F52F, 0, 0, SYSTEM_MS4PLAY,     MAPPER_NONE,   SYSTEM_SMS2,        REGION_USA}, /* BOom (v1.0) */
+  {0x143AB50B, 0, 0, SYSTEM_MS4PLAY,     MAPPER_NONE,   SYSTEM_SMS2,        REGION_USA}, /* BOom (v1.1) */
 
   /* games supporting YM2413 FM */
   {0x1C951F8E, 0, 1, SYSTEM_GAMEPAD,  MAPPER_SEGA,   SYSTEM_SMS2,        REGION_USA}, /* After Burner */
diff --git a/libretro/libretro.c b/libretro/libretro.c
index 8cca6f4..e8b68e5 100644
--- a/libretro/libretro.c
+++ b/libretro/libretro.c
@@ -745,6 +745,8 @@ static void configure_controls(void)
     input.system[1] = SYSTEM_TEAMPLAYER;
   else if (!strcmp(var.value, "teamplayer 1&2"))
     input.system[0] = input.system[1] = SYSTEM_TEAMPLAYER;
+  else if (!strcmp(var.value, "master system 4p"))
+    input.system[0] = SYSTEM_MS4PLAY;
 
   var.key = "portb";
   environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
@@ -768,7 +770,7 @@ void retro_set_environment(retro_environment_t cb)
       { "addr_error", "68k address error; enabled|disabled" },
       { "lock_on", "Cartridge lock-on; disabled|game genie|action replay (pro)|sonic & knuckles" },
       { "padtype", "Gamepad type; auto|6-buttons|3-buttons|2-buttons" },
-      { "multitap", "Multi Tap; disabled|4-wayplay|teamplayer (port 1)|teamplayer (port 2)|teamplayer (both)" },
+      { "multitap", "Multi Tap; disabled|4-wayplay|teamplayer (port 1)|teamplayer (port 2)|teamplayer (both)|master system 4p" },
       { "portb", "Control Port 2; enabled|disabled" },
       { "ym2413", "Master System FM; auto|disabled|enabled" },
       { "dac_bits", "YM2612 DAC quantization; disabled|enabled" },