diff --git a/Core/gb.h b/Core/gb.h
index 0b188d62..3b83b6d2 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -185,7 +185,7 @@ enum {
     // Unfortunately it is not readable or writable after boot has finished, so research of this
     // register is quite limited. The value written to this register, however, can be controlled
     // in some cases.
-    GB_IO_MODE = 0x4c,
+    GB_IO_KEY0 = 0x4c,
 
     /* General CGB features */
     GB_IO_KEY1       = 0x4d, // CGB Mode Only - Prepare Speed Switch
@@ -193,7 +193,7 @@ enum {
     /* Missing */
 
     GB_IO_VBK        = 0x4f, // CGB Mode Only - VRAM Bank
-    GB_IO_BIOS       = 0x50, // Write to disable the BIOS mapping
+    GB_IO_BANK       = 0x50, // Write to disable the BIOS mapping
 
     /* CGB DMA */
     GB_IO_HDMA1      = 0x51, // CGB Mode Only - New DMA Source, High
@@ -212,7 +212,7 @@ enum {
     GB_IO_BGPD       = 0x69, // CGB Mode Only - Background Palette Data
     GB_IO_OBPI       = 0x6a, // CGB Mode Only - Sprite Palette Index
     GB_IO_OBPD       = 0x6b, // CGB Mode Only - Sprite Palette Data
-    GB_IO_OBJECT_PRIORITY = 0x6c, // Affects object priority (X based or index based)
+    GB_IO_OPRI       = 0x6c, // Affects object priority (X based or index based)
 
     /* Missing */
 
diff --git a/Core/memory.c b/Core/memory.c
index 148c9867..27f58e18 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -295,11 +295,11 @@ static uint8_t read_high_memory(GB_gameboy_t *gb, uint16_t addr)
                 return gb->io_registers[GB_IO_TAC] | 0xF8;
             case GB_IO_STAT:
                 return gb->io_registers[GB_IO_STAT] | 0x80;
-            case GB_IO_OBJECT_PRIORITY:
+            case GB_IO_OPRI:
                 if (!GB_is_cgb(gb)) {
                     return 0xFF;
                 }
-                return gb->io_registers[GB_IO_OBJECT_PRIORITY] | 0xFE;
+                return gb->io_registers[GB_IO_OPRI] | 0xFE;
 
             case GB_IO_PCM_12:
                 if (!GB_is_cgb(gb)) return 0xFF;
@@ -663,8 +663,8 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
             case GB_IO_UNKNOWN5:
                 gb->io_registers[addr & 0xFF] = value;
                 return;
-            case GB_IO_OBJECT_PRIORITY:
-                if ((!gb->boot_rom_finished || (gb->io_registers[GB_IO_MODE] & 8)) && GB_is_cgb(gb)) {
+            case GB_IO_OPRI:
+                if ((!gb->boot_rom_finished || (gb->io_registers[GB_IO_KEY0] & 8)) && GB_is_cgb(gb)) {
                     gb->io_registers[addr & 0xFF] = value;
                     gb->object_priority = (value & 1) ? GB_OBJECT_PRIORITY_X : GB_OBJECT_PRIORITY_INDEX;
                 }
@@ -785,14 +785,14 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                 }
                 return;
 
-            case GB_IO_BIOS:
+            case GB_IO_BANK:
                 gb->boot_rom_finished = true;
                 return;
 
-            case GB_IO_MODE:
+            case GB_IO_KEY0:
                 if (GB_is_cgb(gb) && !gb->boot_rom_finished) {
                     gb->cgb_mode = !(value & 0xC); /* The real "contents" of this register aren't quite known yet. */
-                    gb->io_registers[GB_IO_MODE] = value;
+                    gb->io_registers[GB_IO_KEY0] = value;
                 }
                 return;
 
diff --git a/Misc/registers.sym b/Misc/registers.sym
index ea76ab3e..3b31b745 100644
--- a/Misc/registers.sym
+++ b/Misc/registers.sym
@@ -41,10 +41,10 @@
 00:FF49 IO_OBP1
 00:FF4A IO_WY
 00:FF4B IO_WX
-00:FF4C IO_DMG_EMULATION 
+00:FF4C IO_KEY0
 00:FF4D IO_KEY1
 00:FF4F IO_VBK
-00:FF50 IO_BIOS
+00:FF50 IO_BANK
 00:FF51 IO_HDMA1
 00:FF52 IO_HDMA2
 00:FF53 IO_HDMA3
@@ -55,7 +55,7 @@
 00:FF69 IO_BGPD
 00:FF6A IO_OBPI
 00:FF6B IO_OBPD
-00:FF6C IO_OBJECT_PRIORITY
+00:FF6C IO_OPRI
 00:FF70 IO_SVBK
 00:FF72 IO_UNKNOWN2
 00:FF73 IO_UNKNOWN3