diff --git a/CHANGES b/CHANGES
index 31cb9f34e..04a737f93 100644
--- a/CHANGES
+++ b/CHANGES
@@ -20,6 +20,7 @@ Misc:
  - Qt: Prevent savestate window from opening while in multiplayer
  - Qt: Disable menu items in multiplayer that don't make sense to have enabled
  - Qt: Dropping multiplayer windows works more cleanly now
+ - GBA BIOS: Implement RegisterRamReset for SIO registers
 
 0.3.0: (2015-08-16)
 Features:
diff --git a/src/gba/bios.c b/src/gba/bios.c
index a20c5ff59..9ea5b5dc9 100644
--- a/src/gba/bios.c
+++ b/src/gba/bios.c
@@ -63,7 +63,12 @@ static void _RegisterRamReset(struct GBA* gba) {
 		memset(gba->video.oam.raw, 0, SIZE_OAM);
 	}
 	if (registers & 0x20) {
-		GBALog(gba, GBA_LOG_STUB, "RegisterRamReset on SIO unimplemented");
+		cpu->memory.store16(cpu, BASE_IO | REG_SIOCNT, 0x0000, 0);
+		cpu->memory.store16(cpu, BASE_IO | REG_RCNT, RCNT_INITIAL, 0);
+		cpu->memory.store16(cpu, BASE_IO | REG_SIOMLT_SEND, 0, 0);
+		cpu->memory.store16(cpu, BASE_IO | REG_JOYCNT, 0, 0);
+		cpu->memory.store32(cpu, BASE_IO | REG_JOY_RECV, 0, 0);
+		cpu->memory.store32(cpu, BASE_IO | REG_JOY_TRANS, 0, 0);
 	}
 	if (registers & 0x40) {
 		GBALog(gba, GBA_LOG_STUB, "RegisterRamReset on Audio unimplemented");