diff --git a/tier0/memdbg.cpp b/tier0/memdbg.cpp
index e5304869..e59ea1d4 100644
--- a/tier0/memdbg.cpp
+++ b/tier0/memdbg.cpp
@@ -887,7 +887,7 @@ void *CDbgMemAlloc::Expand_NoLongerSupported( void *pMem, size_t nSize )
 //-----------------------------------------------------------------------------
 void CDbgMemAlloc::PushAllocDbgInfo( const char *pFileName, int nLine )
 {
-	if ( g_DbgInfoStack == NULL )
+	if ( g_DbgInfoStack == (void*)NULL )
 	{
 		g_DbgInfoStack = (DbgInfoStack_t *)DebugAlloc( sizeof(DbgInfoStack_t) * DBG_INFO_STACK_DEPTH );
 		g_nDbgInfoStackDepth = -1;
@@ -901,7 +901,7 @@ void CDbgMemAlloc::PushAllocDbgInfo( const char *pFileName, int nLine )
 
 void CDbgMemAlloc::PopAllocDbgInfo()
 {
-	if ( g_DbgInfoStack == NULL )
+	if ( g_DbgInfoStack == (void*)NULL )
 	{
 		g_DbgInfoStack = (DbgInfoStack_t *)DebugAlloc( sizeof(DbgInfoStack_t) * DBG_INFO_STACK_DEPTH );
 		g_nDbgInfoStackDepth = -1;
@@ -922,7 +922,7 @@ uint32 CDbgMemAlloc::GetDebugInfoSize()
 
 void CDbgMemAlloc::SaveDebugInfo( void *pvDebugInfo )
 {
-	if ( g_DbgInfoStack == NULL )
+	if ( g_DbgInfoStack == (void*)NULL )
 	{
 		g_DbgInfoStack = (DbgInfoStack_t *)DebugAlloc( sizeof(DbgInfoStack_t) * DBG_INFO_STACK_DEPTH );
 		g_nDbgInfoStackDepth = -1;
@@ -935,7 +935,7 @@ void CDbgMemAlloc::SaveDebugInfo( void *pvDebugInfo )
 
 void CDbgMemAlloc::RestoreDebugInfo( const void *pvDebugInfo )
 {
-	if ( g_DbgInfoStack == NULL )
+	if ( g_DbgInfoStack == (void*)NULL )
 	{
 		g_DbgInfoStack = (DbgInfoStack_t *)DebugAlloc( sizeof(DbgInfoStack_t) * DBG_INFO_STACK_DEPTH );
 		g_nDbgInfoStackDepth = -1;
@@ -976,7 +976,7 @@ void CDbgMemAlloc::GetActualDbgInfo( const char *&pFileName, int &nLine )
 	return;
 #endif
 
-	if ( g_DbgInfoStack == NULL )
+	if ( g_DbgInfoStack == (void*)NULL )
 	{
 		g_DbgInfoStack = (DbgInfoStack_t *)DebugAlloc( sizeof(DbgInfoStack_t) * DBG_INFO_STACK_DEPTH );
 		g_nDbgInfoStackDepth = -1;