diff --git a/Makefile b/Makefile
index e911a87a6..b0d611fc7 100644
--- a/Makefile
+++ b/Makefile
@@ -68,6 +68,7 @@ $(B_DIR)/lib/ultra/gu/ortho.o: LOOPUNROLL :=
 $(B_DIR)/lib/ultra/libc/ll.o: MIPSISET := -mips3 -o32
 $(B_DIR)/lib/ultra/libc/llcvt.o: MIPSISET := -mips3 -o32
 
+$(B_DIR)/lib/ultra/io/aisetnextbuf.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/io/dpctr.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/io/pigetcmdq.o: OPT_LVL := -O1
 $(B_DIR)/lib/ultra/io/si.o: OPT_LVL := -O1
diff --git a/src/include/lib/lib_51ec0.h b/src/include/lib/lib_51ec0.h
index 18c6f7817..6d8739a5e 100644
--- a/src/include/lib/lib_51ec0.h
+++ b/src/include/lib/lib_51ec0.h
@@ -3,6 +3,6 @@
 #include <ultra64.h>
 #include "types.h"
 
-u32 func00051ec0(void);
+u32 __osAiDeviceBusy(void);
 
 #endif
diff --git a/src/lib/lib_51ec0.c b/src/lib/lib_51ec0.c
index b8d73645d..12d3a8256 100644
--- a/src/lib/lib_51ec0.c
+++ b/src/lib/lib_51ec0.c
@@ -1,7 +1,7 @@
 #include <ultra64.h>
 
 GLOBAL_ASM(
-glabel func00051ec0
+glabel __osAiDeviceBusy
 /*    51ec0:	3c0ea450 */ 	lui	$t6,0xa450
 /*    51ec4:	8dc4000c */ 	lw	$a0,0xc($t6)
 /*    51ec8:	3c018000 */ 	lui	$at,0x8000
diff --git a/src/lib/ultra/io/aisetnextbuf.c b/src/lib/ultra/io/aisetnextbuf.c
index 7d1cea38f..b51c87dcb 100644
--- a/src/lib/ultra/io/aisetnextbuf.c
+++ b/src/lib/ultra/io/aisetnextbuf.c
@@ -28,7 +28,7 @@ glabel osAiSetNextBuffer
 /*    4e414:	3c018006 */ 	lui	$at,%hi(var80060990)
 /*    4e418:	a0200990 */ 	sb	$zero,%lo(var80060990)($at)
 .L0004e41c:
-/*    4e41c:	0c0147b0 */ 	jal	func00051ec0
+/*    4e41c:	0c0147b0 */ 	jal	__osAiDeviceBusy
 /*    4e420:	00000000 */ 	nop
 /*    4e424:	10400003 */ 	beqz	$v0,.L0004e434
 /*    4e428:	00000000 */ 	nop
@@ -52,3 +52,29 @@ glabel osAiSetNextBuffer
 /*    4e468:	00000000 */ 	nop
 /*    4e46c:	00000000 */ 	nop
 );
+
+// Mismatch: Needs data relocation
+//s32 osAiSetNextBuffer(void *bufPtr, u32 size)
+//{
+//	static u8 hdwrBugFlag = 0;
+//	char *bptr = bufPtr;
+//
+//	if (hdwrBugFlag != 0) {
+//		bptr -= 0x2000;
+//	}
+//
+//	if ((((u32)bufPtr + size) & 0x1fff) == 0) {
+//		hdwrBugFlag = 1;
+//	} else {
+//		hdwrBugFlag = 0;
+//	}
+//
+//	if (__osAiDeviceBusy()) {
+//		return -1;
+//	}
+//
+//	IO_WRITE(AI_DRAM_ADDR_REG, osVirtualToPhysical(bptr));
+//	IO_WRITE(AI_LEN_REG, size);
+//
+//	return 0;
+//}