diff --git a/Makefile b/Makefile
index 830cef5a7..5f01da16c 100644
--- a/Makefile
+++ b/Makefile
@@ -75,6 +75,7 @@ $(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
 $(B_DIR)/lib/ultra/os/resetglobalintmask.o: OPT_LVL := -O1
+$(B_DIR)/lib/ultra/os/stopthread.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/thread.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/os/yieldthread.o: OPT_LVL := -O1
 
diff --git a/src/lib/ultra/os/stopthread.c b/src/lib/ultra/os/stopthread.c
index 11a12f720..2218b1d3a 100644
--- a/src/lib/ultra/os/stopthread.c
+++ b/src/lib/ultra/os/stopthread.c
@@ -1,58 +1,28 @@
 #include <libultra_internal.h>
+#include "game/data/data_000000.h"
 
-GLOBAL_ASM(
-glabel osStopThread
-/*    48370:	27bdffc8 */ 	addiu	$sp,$sp,-56
-/*    48374:	afbf0024 */ 	sw	$ra,0x24($sp)
-/*    48378:	afa40038 */ 	sw	$a0,0x38($sp)
-/*    4837c:	afb20020 */ 	sw	$s2,0x20($sp)
-/*    48380:	afb1001c */ 	sw	$s1,0x1c($sp)
-/*    48384:	0c01256c */ 	jal	__osDisableInt
-/*    48388:	afb00018 */ 	sw	$s0,0x18($sp)
-/*    4838c:	8fae0038 */ 	lw	$t6,0x38($sp)
-/*    48390:	00408025 */ 	or	$s0,$v0,$zero
-/*    48394:	15c00003 */ 	bnez	$t6,.L000483a4
-/*    48398:	00000000 */ 	nop
-/*    4839c:	10000003 */ 	b	.L000483ac
-/*    483a0:	24110004 */ 	addiu	$s1,$zero,0x4
-.L000483a4:
-/*    483a4:	8faf0038 */ 	lw	$t7,0x38($sp)
-/*    483a8:	95f10010 */ 	lhu	$s1,0x10($t7)
-.L000483ac:
-/*    483ac:	02209025 */ 	or	$s2,$s1,$zero
-/*    483b0:	24010002 */ 	addiu	$at,$zero,0x2
-/*    483b4:	1241000f */ 	beq	$s2,$at,.L000483f4
-/*    483b8:	24010004 */ 	addiu	$at,$zero,0x4
-/*    483bc:	12410005 */ 	beq	$s2,$at,.L000483d4
-/*    483c0:	24010008 */ 	addiu	$at,$zero,0x8
-/*    483c4:	1241000b */ 	beq	$s2,$at,.L000483f4
-/*    483c8:	00000000 */ 	nop
-/*    483cc:	10000010 */ 	b	.L00048410
-/*    483d0:	00000000 */ 	nop
-.L000483d4:
-/*    483d4:	3c198006 */ 	lui	$t9,%hi(__osRunningThread)
-/*    483d8:	8f390940 */ 	lw	$t9,%lo(__osRunningThread)($t9)
-/*    483dc:	24180001 */ 	addiu	$t8,$zero,0x1
-/*    483e0:	00002025 */ 	or	$a0,$zero,$zero
-/*    483e4:	0c000ee8 */ 	jal	__osEnqueueAndYield
-/*    483e8:	a7380010 */ 	sh	$t8,0x10($t9)
-/*    483ec:	10000008 */ 	b	.L00048410
-/*    483f0:	00000000 */ 	nop
-.L000483f4:
-/*    483f4:	8fa90038 */ 	lw	$t1,0x38($sp)
-/*    483f8:	24080001 */ 	addiu	$t0,$zero,0x1
-/*    483fc:	a5280010 */ 	sh	$t0,0x10($t1)
-/*    48400:	8faa0038 */ 	lw	$t2,0x38($sp)
-/*    48404:	8d440008 */ 	lw	$a0,0x8($t2)
-/*    48408:	0c012884 */ 	jal	__osDequeueThread
-/*    4840c:	01402825 */ 	or	$a1,$t2,$zero
-.L00048410:
-/*    48410:	0c012588 */ 	jal	__osRestoreInt
-/*    48414:	02002025 */ 	or	$a0,$s0,$zero
-/*    48418:	8fbf0024 */ 	lw	$ra,0x24($sp)
-/*    4841c:	8fb00018 */ 	lw	$s0,0x18($sp)
-/*    48420:	8fb1001c */ 	lw	$s1,0x1c($sp)
-/*    48424:	8fb20020 */ 	lw	$s2,0x20($sp)
-/*    48428:	03e00008 */ 	jr	$ra
-/*    4842c:	27bd0038 */ 	addiu	$sp,$sp,0x38
-);
+void osStopThread(OSThread *t)
+{
+	register u32 saveMask = __osDisableInt();
+	register u16 state;
+
+	if (t == NULL) {
+		state = OS_STATE_RUNNING;
+	} else {
+		state = t->state;
+	}
+
+	switch (state) {
+	case OS_STATE_RUNNING:
+		__osRunningThread->state = OS_STATE_STOPPED;
+		__osEnqueueAndYield(NULL);
+		break;
+	case OS_STATE_RUNNABLE:
+	case OS_STATE_WAITING:
+		t->state = OS_STATE_STOPPED;
+		__osDequeueThread(t->queue, t);
+		break;
+	}
+
+	__osRestoreInt(saveMask);
+}