diff --git a/Makefile.common b/Makefile.common
index 88a46ff..4012987 100644
--- a/Makefile.common
+++ b/Makefile.common
@@ -11,7 +11,7 @@ COREDEFINES += -DPSS_STYLE=1
 endif
 
 ifeq ($(TUP_CWD),)
-FCEU_SRC_DIRS := $(CORE_DIR)/boards $(CORE_DIR)/input
+FCEU_SRC_DIRS := $(CORE_DIR)/boards $(CORE_DIR)/input $(CORE_DIR)/mappers
 SOURCES_C     := $(foreach dir,$(FCEU_SRC_DIRS),$(wildcard $(dir)/*.c))
 else
 SOURCES_C = $(CORE_DIR)/boards/*.c $(CORE_DIR)/input/*.c
diff --git a/src/boards/237.c b/src/boards/237.c
new file mode 100644
index 0000000..e2b784a
--- /dev/null
+++ b/src/boards/237.c
@@ -0,0 +1,91 @@
+/* FCEUmm - NES/Famicom Emulator
+ *
+ * Copyright notice for this file:
+ *  Copyright (C) 2019 Libretro Team
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+/* Mapper 237 - "Teletubbies / Y2K" 420-in-1 pirate multicart.
+ * Dipswitch settings:
+ * 0: 42-in-1
+ * 1: 5,000-in-1
+ * 2: 420-in-1
+ * 3: 10,000,000-in-1 (lol)
+ */
+
+#include "mapinc.h"
+
+static uint8 reg[2];
+static uint8 dipswitch;
+
+static SFORMAT StateRegs[] =
+{
+	{ &reg[0],    1, "REG0" },
+	{ &reg[1],    1, "REG1" },
+	{ &dipswitch, 1, "DPSW" },
+	{ 0 }
+};
+
+static void Sync(void) {
+	uint8 bank = (reg[1] & 0x07);
+	uint8 base = (reg[1] & 0x18) | ((reg[0] & 0x04) << 3);
+	uint8 mode = (reg[1] & 0xC0) >> 6;
+
+	setchr8(0);
+	setprg16(0x8000, base | (bank & ~(mode & 1)));
+	setprg16(0xC000, base | ((mode & 0x02) ? (bank | (mode & 0x01)) : 0x07));
+	setmirror(((reg[1] & 0x20) >> 5) ^ 1);
+}
+
+static DECLFW(M237Write) {
+	if (!(reg[0] & 0x02)) {
+		reg[0] = A & 0x0F;
+		reg[1] = (reg[1] & 0x07) | (V & 0xF8);
+	}
+	reg[1] = (reg[1] & 0xF8) | (V & 0x07);
+	Sync();
+}
+
+static DECLFR(M237Read) {
+	if (!(reg[0] & 0x02) && (reg[0] & 0x01))
+		return dipswitch;
+	return CartBR(A);
+}
+
+static void M237Power(void) {
+	Sync();
+	SetReadHandler (0x8000, 0xFFFF, M237Read);
+	SetWriteHandler(0x8000, 0xFFFF, M237Write);
+}
+
+static void M237Reset(void) {
+	reg[0] = reg[1] = 0;
+	Sync();
+}
+
+static void StateRestore(int version) {
+	Sync();
+}
+
+void Mapper237_Init(CartInfo *info) {
+	dipswitch = 0;
+	if ((info->CRC32) == 0x272709b9) /* Teletubbies Y2K (420-in-1) */
+		dipswitch = 2;
+	info->Power = M237Power;
+	info->Reset = M237Reset;
+	GameStateRestore = StateRestore;
+	AddExState(&StateRegs, ~0, 0, 0);
+}
diff --git a/src/ines-correct.h b/src/ines-correct.h
index e26aa65..85a8dbe 100644
--- a/src/ines-correct.h
+++ b/src/ines-correct.h
@@ -353,6 +353,7 @@
 	{0x071e4ee8,    114,        0}, /* m114,submapper 1 test rom */
 	{0xfe3e03a1,    197,       -1}, /* Mortal Kombat III Special (YY-030) (Ch) [!] */
 	{0x9151d311,    197,       -1}, /* Mortal Kombat III 28 Peoples (NT-328) (Ch) [!] */
+	{0x272709b9,    237,       -1}, /* Teletubbies Y2K (420-in-1) */
 
 	/* ines mappers that uses iNes 2.0 numbers */
 
diff --git a/src/ines.c b/src/ines.c
index 8edac57..656337a 100644
--- a/src/ines.c
+++ b/src/ines.c
@@ -629,7 +629,7 @@ static BMAPPINGLocal bmap[] = {
 	{(uint8_t*)"BMC MAXI",			234, Mapper234_Init},
 	{(uint8_t*)"",					235, Mapper235_Init},
 /*	{(uint8_t*)"",					236, Mapper236_Init}, */
-/*	{(uint8_t*)"",					237, Mapper237_Init}, */
+	{(uint8_t*)"Teletubbies / Y2K",	237, Mapper237_Init},
 	{(uint8_t*)"UNL6035052",			238, UNL6035052_Init},
 /*	{(uint8_t*)"",					239, Mapper239_Init}, */
 	{(uint8_t*)"",					240, Mapper240_Init},