diff --git a/Makefile b/Makefile
index 2aaae374a..e89ff46ca 100644
--- a/Makefile
+++ b/Makefile
@@ -102,6 +102,7 @@ $(B_DIR)/lib/ultra/os/resetglobalintmask.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/sendmesg.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/seteventmesg.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/setthreadpri.o: OPT_LVL := -O1
+$(B_DIR)/lib/ultra/os/settimer.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/startthread.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/stopthread.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/stoptimer.o: OPT_LVL := -O1
diff --git a/src/include/PR/os_time.h b/src/include/PR/os_time.h
index b8b34db16..5020599f4 100644
--- a/src/include/PR/os_time.h
+++ b/src/include/PR/os_time.h
@@ -20,6 +20,6 @@ typedef u64 OSTime;
 
 OSTime osGetTime(void);
 void osSetTime(OSTime time);
-u32 osSetTimer(OSTimer *, OSTime, u64, OSMesgQueue *, OSMesg);
+int osSetTimer(OSTimer *t, OSTime value, OSTime interval, OSMesgQueue *mq, OSMesg msg);
 
 #endif
diff --git a/src/lib/ultra/os/settimer.c b/src/lib/ultra/os/settimer.c
index 1d93aa2dd..cf9a92f58 100644
--- a/src/lib/ultra/os/settimer.c
+++ b/src/lib/ultra/os/settimer.c
@@ -1,65 +1,27 @@
 #include <libultra_internal.h>
+#include "game/data/data_000000.h"
 
-GLOBAL_ASM(
-glabel osSetTimer
-/*    48b20:	27bdffe0 */ 	addiu	$sp,$sp,-32
-/*    48b24:	afa40020 */ 	sw	$a0,0x20($sp)
-/*    48b28:	8fae0020 */ 	lw	$t6,0x20($sp)
-/*    48b2c:	afbf0014 */ 	sw	$ra,0x14($sp)
-/*    48b30:	afa60028 */ 	sw	$a2,0x28($sp)
-/*    48b34:	afa7002c */ 	sw	$a3,0x2c($sp)
-/*    48b38:	adc00000 */ 	sw	$zero,0x0($t6)
-/*    48b3c:	8faf0020 */ 	lw	$t7,0x20($sp)
-/*    48b40:	ade00004 */ 	sw	$zero,0x4($t7)
-/*    48b44:	8fa80020 */ 	lw	$t0,0x20($sp)
-/*    48b48:	8fb90034 */ 	lw	$t9,0x34($sp)
-/*    48b4c:	8fb80030 */ 	lw	$t8,0x30($sp)
-/*    48b50:	ad19000c */ 	sw	$t9,0xc($t0)
-/*    48b54:	ad180008 */ 	sw	$t8,0x8($t0)
-/*    48b58:	8faa0028 */ 	lw	$t2,0x28($sp)
-/*    48b5c:	8fab002c */ 	lw	$t3,0x2c($sp)
-/*    48b60:	15400003 */ 	bnez	$t2,.L00048b70
-/*    48b64:	00000000 */ 	nop
-/*    48b68:	11600005 */ 	beqz	$t3,.L00048b80
-/*    48b6c:	00000000 */ 	nop
-.L00048b70:
-/*    48b70:	8fa90020 */ 	lw	$t1,0x20($sp)
-/*    48b74:	ad2a0010 */ 	sw	$t2,0x10($t1)
-/*    48b78:	10000006 */ 	b	.L00048b94
-/*    48b7c:	ad2b0014 */ 	sw	$t3,0x14($t1)
-.L00048b80:
-/*    48b80:	8fae0020 */ 	lw	$t6,0x20($sp)
-/*    48b84:	8fac0030 */ 	lw	$t4,0x30($sp)
-/*    48b88:	8fad0034 */ 	lw	$t5,0x34($sp)
-/*    48b8c:	adcc0010 */ 	sw	$t4,0x10($t6)
-/*    48b90:	adcd0014 */ 	sw	$t5,0x14($t6)
-.L00048b94:
-/*    48b94:	8faf0038 */ 	lw	$t7,0x38($sp)
-/*    48b98:	8fb80020 */ 	lw	$t8,0x20($sp)
-/*    48b9c:	af0f0018 */ 	sw	$t7,0x18($t8)
-/*    48ba0:	8fa80020 */ 	lw	$t0,0x20($sp)
-/*    48ba4:	8fb9003c */ 	lw	$t9,0x3c($sp)
-/*    48ba8:	ad19001c */ 	sw	$t9,0x1c($t0)
-/*    48bac:	0c01250a */ 	jal	__osInsertTimer
-/*    48bb0:	8fa40020 */ 	lw	$a0,0x20($sp)
-/*    48bb4:	3c0a8006 */ 	lui	$t2,%hi(__osTimerList)
-/*    48bb8:	8d4a08a0 */ 	lw	$t2,%lo(__osTimerList)($t2)
-/*    48bbc:	afa20018 */ 	sw	$v0,0x18($sp)
-/*    48bc0:	afa3001c */ 	sw	$v1,0x1c($sp)
-/*    48bc4:	8fa90020 */ 	lw	$t1,0x20($sp)
-/*    48bc8:	8d4b0000 */ 	lw	$t3,0x0($t2)
-/*    48bcc:	15690004 */ 	bne	$t3,$t1,.L00048be0
-/*    48bd0:	00000000 */ 	nop
-/*    48bd4:	8fa40018 */ 	lw	$a0,0x18($sp)
-/*    48bd8:	0c0124ed */ 	jal	__osSetTimerIntr
-/*    48bdc:	8fa5001c */ 	lw	$a1,0x1c($sp)
-.L00048be0:
-/*    48be0:	8fbf0014 */ 	lw	$ra,0x14($sp)
-/*    48be4:	27bd0020 */ 	addiu	$sp,$sp,0x20
-/*    48be8:	00001025 */ 	or	$v0,$zero,$zero
-/*    48bec:	03e00008 */ 	jr	$ra
-/*    48bf0:	00000000 */ 	nop
-/*    48bf4:	00000000 */ 	nop
-/*    48bf8:	00000000 */ 	nop
-/*    48bfc:	00000000 */ 	nop
-);
+int osSetTimer(OSTimer *t, OSTime value, OSTime interval, OSMesgQueue *mq, OSMesg msg)
+{
+	OSTime time;
+
+	t->next = NULL;
+	t->prev = NULL;
+	t->interval = interval;
+
+	if (value != 0) {
+		t->remaining = value;
+	} else {
+		t->remaining = interval;
+	}
+
+	t->mq = mq;
+	t->msg = msg;
+	time = __osInsertTimer(t);
+
+	if (__osTimerList->next == t) {
+		__osSetTimerIntr(time);
+	}
+
+	return 0;
+}