diff --git a/pyboy/core/cartridge/base_mbc.pxd b/pyboy/core/cartridge/base_mbc.pxd
index db1254c10..4ed1d3cf8 100644
--- a/pyboy/core/cartridge/base_mbc.pxd
+++ b/pyboy/core/cartridge/base_mbc.pxd
@@ -3,7 +3,7 @@
 # GitHub: https://github.com/Baekalfen/PyBoy
 #
 
-from libc.stdint cimport uint8_t, uint16_t, uint32_t
+from libc.stdint cimport uint8_t, uint16_t, uint32_t, uint64_t
 
 from pyboy.core.cartridge.rtc cimport RTC
 from pyboy.logging.logging cimport Logger
@@ -29,7 +29,7 @@ cdef class BaseMBC:
     cdef uint16_t rambank_selected
     cdef uint16_t rombank_selected
     cdef uint8_t[:] rombank_view
-    cdef uint8_t[:] rambank_view 
+    cdef uint8_t[:] rambank_view
     cdef bint cgb
 
     cdef void save_state(self, IntIOInterface) noexcept
@@ -39,9 +39,9 @@ cdef class BaseMBC:
     cdef void init_rambanks(self, uint8_t) noexcept
     cdef str getgamename(self, uint8_t[:,:]) noexcept
 
-    cdef uint8_t getitem(self, uint16_t) noexcept nogil
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef uint8_t getitem(self, uint64_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
     cdef void overrideitem(self, int, uint16_t, uint8_t) noexcept nogil
 
 cdef class ROMOnly(BaseMBC):
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
diff --git a/pyboy/core/cartridge/mbc1.pxd b/pyboy/core/cartridge/mbc1.pxd
index f4b54e372..a039ac859 100644
--- a/pyboy/core/cartridge/mbc1.pxd
+++ b/pyboy/core/cartridge/mbc1.pxd
@@ -3,16 +3,14 @@
 # GitHub: https://github.com/Baekalfen/PyBoy
 #
 
-from libc.stdint cimport uint8_t, uint16_t
-
 from pyboy.logging.logging cimport Logger
-
+from libc.stdint cimport uint8_t, uint16_t, uint64_t
 from .base_mbc cimport BaseMBC
 
 
 cdef Logger logger
 
 cdef class MBC1(BaseMBC):
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
     cdef uint8_t bank_select_register1
     cdef uint8_t bank_select_register2
diff --git a/pyboy/core/cartridge/mbc2.pxd b/pyboy/core/cartridge/mbc2.pxd
index 2006f7454..2bfc2945b 100644
--- a/pyboy/core/cartridge/mbc2.pxd
+++ b/pyboy/core/cartridge/mbc2.pxd
@@ -3,14 +3,12 @@
 # GitHub: https://github.com/Baekalfen/PyBoy
 #
 
-from libc.stdint cimport uint8_t, uint16_t
-
 from pyboy.logging.logging cimport Logger
-
+from libc.stdint cimport uint8_t, uint16_t, uint64_t
 from .base_mbc cimport BaseMBC
 
 
 cdef Logger logger
 
 cdef class MBC2(BaseMBC):
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
diff --git a/pyboy/core/cartridge/mbc3.pxd b/pyboy/core/cartridge/mbc3.pxd
index a0469da3d..a68ca7699 100644
--- a/pyboy/core/cartridge/mbc3.pxd
+++ b/pyboy/core/cartridge/mbc3.pxd
@@ -3,14 +3,13 @@
 # GitHub: https://github.com/Baekalfen/PyBoy
 #
 
-from libc.stdint cimport uint8_t, uint16_t
-
 from pyboy.logging.logging cimport Logger
 
+from libc.stdint cimport uint8_t, uint16_t, uint64_t
 from .base_mbc cimport BaseMBC
 
 
 cdef Logger logger
 
 cdef class MBC3(BaseMBC):
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
diff --git a/pyboy/core/cartridge/mbc5.pxd b/pyboy/core/cartridge/mbc5.pxd
index 1adcdd904..03eb964fe 100644
--- a/pyboy/core/cartridge/mbc5.pxd
+++ b/pyboy/core/cartridge/mbc5.pxd
@@ -3,14 +3,14 @@
 # GitHub: https://github.com/Baekalfen/PyBoy
 #
 
-from libc.stdint cimport uint8_t, uint16_t
 
 from pyboy.logging.logging cimport Logger
 
+from libc.stdint cimport uint8_t, uint16_t, uint64_t
 from .base_mbc cimport BaseMBC
 
 
 cdef Logger logger
 
 cdef class MBC5(BaseMBC):
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
diff --git a/pyboy/core/mb.pxd b/pyboy/core/mb.pxd
index 0b176b4d3..df96d080e 100644
--- a/pyboy/core/mb.pxd
+++ b/pyboy/core/mb.pxd
@@ -71,8 +71,8 @@ cdef class Motherboard:
     @cython.locals(pc=cython.int, bank=cython.int)
     cdef bint breakpoint_reached(self) noexcept with gil
 
-    cdef uint8_t getitem(self, uint16_t) noexcept nogil
-    cdef void setitem(self, uint16_t, uint8_t) noexcept nogil
+    cdef uint8_t getitem(self, uint64_t) noexcept nogil
+    cdef void setitem(self, uint64_t, uint8_t) noexcept nogil
 
     @cython.locals(offset=cython.int, dst=cython.int, n=cython.int)
     cdef void transfer_DMA(self, uint8_t) noexcept nogil
diff --git a/pyboy/core/opcodes.pxd b/pyboy/core/opcodes.pxd
index aacc77a08..6ff060d1f 100644
--- a/pyboy/core/opcodes.pxd
+++ b/pyboy/core/opcodes.pxd
@@ -3,22 +3,19 @@
 # DO NOT MODIFY THIS FILE.
 # CHANGES TO THE CODE SHOULD BE MADE IN 'opcodes_gen.py'.
 
+from . cimport cpu
 cimport cython
 from libc.stdint cimport uint8_t, uint16_t, uint32_t
 
 from pyboy.logging.logging cimport Logger
-
-from . cimport cpu
-
-
 cdef Logger logger
 
 cdef uint16_t FLAGC, FLAGH, FLAGN, FLAGZ
 cdef uint8_t[512] OPCODE_LENGTHS
-@cython.locals(v=uint16_t, a=uint16_t, b=uint16_t, pc=uint16_t, oplen=uint8_t)
-cdef int execute_opcode(cpu.CPU, uint16_t) noexcept nogil
-cdef uint8_t no_opcode(cpu.CPU) noexcept nogil
+@cython.locals(v=cython.int, a=cython.int, b=cython.int, pc=cython.ushort)
+cdef int execute_opcode(cpu.CPU, uint64_t) noexcept nogil
 
+cdef uint8_t no_opcode(cpu.CPU) noexcept nogil
 @cython.locals(v=int, flag=uint8_t, t=int)
 cdef uint8_t NOP_00(cpu.CPU) noexcept nogil # 00 NOP
 @cython.locals(v=int, flag=uint8_t, t=int)
diff --git a/pyboy/core/opcodes.py b/pyboy/core/opcodes.py
index 1762144ff..0d97c9b95 100644
--- a/pyboy/core/opcodes.py
+++ b/pyboy/core/opcodes.py
@@ -2166,7 +2166,7 @@ def JP_CA(cpu, v): # CA JP Z,a16
 
 
 def PREFIX_CB(cpu): # CB PREFIX CB
-    logger.critical("CB cannot be called!")
+    logger.critical('CB cannot be called!')
     cpu.PC += 1
     cpu.PC &= 0xFFFF
     return 4
diff --git a/pyboy/core/opcodes_gen.py b/pyboy/core/opcodes_gen.py
index 90566067f..84beab668 100644
--- a/pyboy/core/opcodes_gen.py
+++ b/pyboy/core/opcodes_gen.py
@@ -39,7 +39,7 @@
 cdef uint16_t FLAGC, FLAGH, FLAGN, FLAGZ
 cdef uint8_t[512] OPCODE_LENGTHS
 @cython.locals(v=cython.int, a=cython.int, b=cython.int, pc=cython.ushort)
-cdef int execute_opcode(cpu.CPU, uint16_t) noexcept nogil
+cdef int execute_opcode(cpu.CPU, uint64_t) noexcept nogil
 
 cdef uint8_t no_opcode(cpu.CPU) noexcept nogil
 """