diff --git a/Makefile b/Makefile
index 24dc88c67..fbedfe146 100644
--- a/Makefile
+++ b/Makefile
@@ -79,6 +79,7 @@ $(B_DIR)/lib/ultra/io/vigetcurrframebuf.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/io/vigetnextframebuf.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/io/visetevent.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/destroythread.o: OPT_LVL := -O1
+$(B_DIR)/lib/ultra/os/jammesg.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/resetglobalintmask.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/setthreadpri.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/startthread.o: OPT_LVL := -O1
diff --git a/src/lib/ultra/os/jammesg.c b/src/lib/ultra/os/jammesg.c
index 85a6288f0..f1fe76c40 100644
--- a/src/lib/ultra/os/jammesg.c
+++ b/src/lib/ultra/os/jammesg.c
@@ -1,97 +1,29 @@
 #include <libultra_internal.h>
+#include "game/data/data_000000.h"
 
-GLOBAL_ASM(
-glabel osJamMesg
-/*    51ef0:	27bdffd8 */ 	addiu	$sp,$sp,-40
-/*    51ef4:	afbf001c */ 	sw	$ra,0x1c($sp)
-/*    51ef8:	afa40028 */ 	sw	$a0,0x28($sp)
-/*    51efc:	afa5002c */ 	sw	$a1,0x2c($sp)
-/*    51f00:	afa60030 */ 	sw	$a2,0x30($sp)
-/*    51f04:	afb10018 */ 	sw	$s1,0x18($sp)
-/*    51f08:	0c01256c */ 	jal	__osDisableInt
-/*    51f0c:	afb00014 */ 	sw	$s0,0x14($sp)
-/*    51f10:	8fae0028 */ 	lw	$t6,0x28($sp)
-/*    51f14:	00408025 */ 	or	$s0,$v0,$zero
-/*    51f18:	8dcf0008 */ 	lw	$t7,0x8($t6)
-/*    51f1c:	8dd80010 */ 	lw	$t8,0x10($t6)
-/*    51f20:	01f8082a */ 	slt	$at,$t7,$t8
-/*    51f24:	14200018 */ 	bnez	$at,.L00051f88
-/*    51f28:	00000000 */ 	nop
-.L00051f2c:
-/*    51f2c:	8fb90030 */ 	lw	$t9,0x30($sp)
-/*    51f30:	24010001 */ 	addiu	$at,$zero,0x1
-/*    51f34:	1721000a */ 	bne	$t9,$at,.L00051f60
-/*    51f38:	00000000 */ 	nop
-/*    51f3c:	3c098006 */ 	lui	$t1,%hi(__osRunningThread)
-/*    51f40:	8d290940 */ 	lw	$t1,%lo(__osRunningThread)($t1)
-/*    51f44:	24080008 */ 	addiu	$t0,$zero,0x8
-/*    51f48:	a5280010 */ 	sh	$t0,0x10($t1)
-/*    51f4c:	8fa40028 */ 	lw	$a0,0x28($sp)
-/*    51f50:	0c000ee8 */ 	jal	__osEnqueueAndYield
-/*    51f54:	24840004 */ 	addiu	$a0,$a0,0x4
-/*    51f58:	10000005 */ 	b	.L00051f70
-/*    51f5c:	00000000 */ 	nop
-.L00051f60:
-/*    51f60:	0c012588 */ 	jal	__osRestoreInt
-/*    51f64:	02002025 */ 	or	$a0,$s0,$zero
-/*    51f68:	10000030 */ 	b	.L0005202c
-/*    51f6c:	2402ffff */ 	addiu	$v0,$zero,-1
-.L00051f70:
-/*    51f70:	8faa0028 */ 	lw	$t2,0x28($sp)
-/*    51f74:	8d4b0008 */ 	lw	$t3,0x8($t2)
-/*    51f78:	8d4c0010 */ 	lw	$t4,0x10($t2)
-/*    51f7c:	016c082a */ 	slt	$at,$t3,$t4
-/*    51f80:	1020ffea */ 	beqz	$at,.L00051f2c
-/*    51f84:	00000000 */ 	nop
-.L00051f88:
-/*    51f88:	8fad0028 */ 	lw	$t5,0x28($sp)
-/*    51f8c:	8dae000c */ 	lw	$t6,0xc($t5)
-/*    51f90:	8daf0010 */ 	lw	$t7,0x10($t5)
-/*    51f94:	01cfc021 */ 	addu	$t8,$t6,$t7
-/*    51f98:	2719ffff */ 	addiu	$t9,$t8,-1
-/*    51f9c:	032f001a */ 	div	$zero,$t9,$t7
-/*    51fa0:	00004010 */ 	mfhi	$t0
-/*    51fa4:	ada8000c */ 	sw	$t0,0xc($t5)
-/*    51fa8:	8faa0028 */ 	lw	$t2,0x28($sp)
-/*    51fac:	8fa9002c */ 	lw	$t1,0x2c($sp)
-/*    51fb0:	15e00002 */ 	bnez	$t7,.L00051fbc
-/*    51fb4:	00000000 */ 	nop
-/*    51fb8:	0007000d */ 	break	0x7
-.L00051fbc:
-/*    51fbc:	2401ffff */ 	addiu	$at,$zero,-1
-/*    51fc0:	15e10004 */ 	bne	$t7,$at,.L00051fd4
-/*    51fc4:	3c018000 */ 	lui	$at,0x8000
-/*    51fc8:	17210002 */ 	bne	$t9,$at,.L00051fd4
-/*    51fcc:	00000000 */ 	nop
-/*    51fd0:	0006000d */ 	break	0x6
-.L00051fd4:
-/*    51fd4:	8d4c000c */ 	lw	$t4,0xc($t2)
-/*    51fd8:	8d4b0014 */ 	lw	$t3,0x14($t2)
-/*    51fdc:	000c7080 */ 	sll	$t6,$t4,0x2
-/*    51fe0:	016ec021 */ 	addu	$t8,$t3,$t6
-/*    51fe4:	af090000 */ 	sw	$t1,0x0($t8)
-/*    51fe8:	8fb90028 */ 	lw	$t9,0x28($sp)
-/*    51fec:	8f2f0008 */ 	lw	$t7,0x8($t9)
-/*    51ff0:	25e80001 */ 	addiu	$t0,$t7,0x1
-/*    51ff4:	af280008 */ 	sw	$t0,0x8($t9)
-/*    51ff8:	8fad0028 */ 	lw	$t5,0x28($sp)
-/*    51ffc:	8daa0000 */ 	lw	$t2,0x0($t5)
-/*    52000:	8d4c0000 */ 	lw	$t4,0x0($t2)
-/*    52004:	11800006 */ 	beqz	$t4,.L00052020
-/*    52008:	00000000 */ 	nop
-/*    5200c:	0c000f40 */ 	jal	__osPopThread
-/*    52010:	01a02025 */ 	or	$a0,$t5,$zero
-/*    52014:	00408825 */ 	or	$s1,$v0,$zero
-/*    52018:	0c01207c */ 	jal	osStartThread
-/*    5201c:	02202025 */ 	or	$a0,$s1,$zero
-.L00052020:
-/*    52020:	0c012588 */ 	jal	__osRestoreInt
-/*    52024:	02002025 */ 	or	$a0,$s0,$zero
-/*    52028:	00001025 */ 	or	$v0,$zero,$zero
-.L0005202c:
-/*    5202c:	8fbf001c */ 	lw	$ra,0x1c($sp)
-/*    52030:	8fb00014 */ 	lw	$s0,0x14($sp)
-/*    52034:	8fb10018 */ 	lw	$s1,0x18($sp)
-/*    52038:	03e00008 */ 	jr	$ra
-/*    5203c:	27bd0028 */ 	addiu	$sp,$sp,0x28
-);
+s32 osJamMesg(OSMesgQueue *mq, OSMesg msg, s32 flag)
+{
+	register u32 saveMask = __osDisableInt();
+
+	while (mq->validCount >= mq->msgCount) {
+		if (flag == OS_MESG_BLOCK) {
+			__osRunningThread->state = OS_STATE_WAITING;
+			__osEnqueueAndYield(&mq->fullqueue);
+		} else {
+			__osRestoreInt(saveMask);
+			return -1;
+		}
+	}
+
+	mq->first = (mq->first + mq->msgCount - 1) % mq->msgCount;
+	mq->msg[mq->first] = msg;
+	mq->validCount++;
+
+	if (mq->mtqueue->next != NULL) {
+		osStartThread(__osPopThread(&mq->mtqueue));
+	}
+
+	__osRestoreInt(saveMask);
+
+	return 0;
+}