diff --git a/include/PR/os_system.h b/include/PR/os_system.h
index 1179189a2..993935352 100644
--- a/include/PR/os_system.h
+++ b/include/PR/os_system.h
@@ -21,7 +21,7 @@
 
 /*---------------------------------------------------------------------*
         Copyright (C) 1998 Nintendo. (Originated by SGI)
-        
+
         $RCSfile: os_system.h,v $
         $Revision: 1.1 $
         $Date: 1998/10/09 08:01:18 $
@@ -54,7 +54,7 @@ extern "C" {
  */
 
 /*
- * Values for osTvType 
+ * Values for osTvType
  */
 #define	OS_TV_PAL		0
 #define	OS_TV_NTSC		1
@@ -103,7 +103,6 @@ extern OSIntMask __OSGlobalIntMask;	/* global interrupt mask */
 
 extern void		osInitialize(void);
 extern void		osExit(void);
-extern u32 		osGetMemSize(void);
 
 /* pre-NMI */
 extern s32		osAfterPreNMI(void);
diff --git a/src/include/lib/boot.h b/src/include/lib/boot.h
index d5bf53e3f..c82118d5f 100644
--- a/src/include/lib/boot.h
+++ b/src/include/lib/boot.h
@@ -2,8 +2,13 @@
 #define _IN_LIB_BOOT_H
 #include <ultra64.h>
 
+#if VERSION >= VERSION_NTSC_1_0
+extern s32 osGetMemSize(void);
+#else
+extern u32 osGetMemSize(void);
+#endif
+
 void boot(void);
-s32 boot_get_mem_size(void);
 void *boot_allocate_stack(s32 threadid, s32 size);
 void boot_check_stack_overflow(void);
 
diff --git a/src/lib/boot.c b/src/lib/boot.c
index 53bf5c9c5..8bc461df2 100644
--- a/src/lib/boot.c
+++ b/src/lib/boot.c
@@ -29,7 +29,7 @@ u32 var8008dbcc;
 OSSched g_Sched;
 OSScClient g_MainSchedClient;
 #if VERSION >= VERSION_NTSC_1_0
-u32 g_OsMemSize;
+u32 g_SavedOsMemSize;
 #else
 u16 *var800902e4;
 u16 var800902e8;
@@ -54,9 +54,9 @@ extern u8 *_inflateSegmentRomStart;
 extern u8 *_inflateSegmentRomEnd;
 
 #if VERSION >= VERSION_NTSC_1_0
-s32 boot_get_mem_size(void)
+s32 osGetMemSize(void)
 {
-	return g_OsMemSize;
+	return g_SavedOsMemSize;
 }
 #endif
 
@@ -89,10 +89,15 @@ void boot(void)
 	u32 flags;
 
 #if VERSION >= VERSION_NTSC_1_0
+	// In NTSC beta, libultra's osGetMemSize is used several times during boot.
+	// This function writes to the expansion area but this shouldn't be a problem...
+	// In NTSC 1.0 and later, libultra's osGetMemSize is not linked and is replaced
+	// with one which returns osMemSize. But it appears as though osMemSize is only
+	// reliable on a cold boot, because it's saved and reloaded here on a reset.
 	if (osResetType == RESETTYPE_WARM) {
-		g_OsMemSize = *(u32 *) STACK_START;
+		g_SavedOsMemSize = *(u32 *) STACK_START;
 	} else {
-		*(u32 *) STACK_START = g_OsMemSize = osMemSize;
+		*(u32 *) STACK_START = g_SavedOsMemSize = osMemSize;
 	}
 #endif
 
diff --git a/src/lib/main.c b/src/lib/main.c
index 4f7b46d4e..26d74565b 100644
--- a/src/lib/main.c
+++ b/src/lib/main.c
@@ -404,7 +404,7 @@ void main_init(void)
 		// In 4MB mode, place it close to the end of memory,
 		// but before the thread stacks and VM system.
 		// In 8MB mode, put it at the end of the expansion pak.
-		if (boot_get_mem_size() <= 4 * 1024 * 1024) {
+		if (osGetMemSize() <= 4 * 1024 * 1024) {
 			addr = K0BASE + 4 * 1024 * 1024;
 			addr -= STACKSIZE_MAIN;
 			addr -= STACKSIZE_IDLE;
diff --git a/src/lib/memp.c b/src/lib/memp.c
index 3dd8ee694..434329f4f 100644
--- a/src/lib/memp.c
+++ b/src/lib/memp.c
@@ -90,18 +90,9 @@ void memp_set_heap(u8 *heapstart, u32 heaplen)
 	g_MempOnboardPools[MEMPOOL_STAGE].rightpos = heapstart + heaplen;
 
 	// If 8MB, reserve the entire expansion pak for the stage pool
-#if VERSION >= VERSION_NTSC_1_0
-	extraend = (u8 *) K0BASE + boot_get_mem_size();
-#else
 	extraend = (u8 *) K0BASE + osGetMemSize();
-#endif
 
-#if VERSION >= VERSION_NTSC_1_0
-	if (boot_get_mem_size() > 4 * 1024 * 1024)
-#else
-	if (osGetMemSize() > 4 * 1024 * 1024)
-#endif
-	{
+	if (osGetMemSize() > 4 * 1024 * 1024) {
 		g_MempExpansionPools[MEMPOOL_STAGE].start = (u8 *) K0BASE + 4 * 1024 * 1024;
 		g_MempExpansionPools[MEMPOOL_STAGE].rightpos = extraend;
 	}
diff --git a/src/lib/vminit.c b/src/lib/vminit.c
index 2cbb0d0fb..be0f31035 100644
--- a/src/lib/vminit.c
+++ b/src/lib/vminit.c
@@ -199,12 +199,7 @@ void vm_init(void)
 
 	rzip_init();
 
-#if VERSION >= VERSION_NTSC_1_0
-	if (boot_get_mem_size() <= 0x400000)
-#else
-	if (osGetMemSize() <= 0x400000)
-#endif
-	{
+	if (osGetMemSize() <= 0x400000) {
 		g_Is4Mb = true;
 
 		g_VmNumPages = (s32)((&_gameSegmentEnd - &_gameSegmentStart) + (VM_PAGE_SIZE - 1)) / VM_PAGE_SIZE;