diff --git a/Core/gb.h b/Core/gb.h
index bd1a18f..6df6999 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -239,6 +239,7 @@ enum {
     /* Missing */
 
     GB_IO_SVBK       = 0x70, // CGB Mode Only - WRAM Bank
+    GB_IO_PSM        = 0x71, // Palette Selection Mode, controls the PSW and key combo
     GB_IO_PSWX       = 0x72, // X position of the palette switching window
     GB_IO_PSWY       = 0x73, // Y position of the palette switching window
     GB_IO_PSW        = 0x74, // Key combo to trigger the palette switching window
diff --git a/Misc/registers.sym b/Misc/registers.sym
index affe663..58fff3e 100644
--- a/Misc/registers.sym
+++ b/Misc/registers.sym
@@ -57,6 +57,7 @@
 00:FF6B IO_OBPD
 00:FF6C IO_OPRI
 00:FF70 IO_SVBK
+00:FF71 IO_PSM
 00:FF72 IO_PSWX
 00:FF73 IO_PSWY
 00:FF74 IO_PSW