diff --git a/public/tier1/characterset.h b/public/tier1/characterset.h
index 6465893e..a1863d0b 100644
--- a/public/tier1/characterset.h
+++ b/public/tier1/characterset.h
@@ -1,4 +1,4 @@
-//===== Copyright © 1996-2005, Valve Corporation, All rights reserved. ======//
+//===== Copyright � 1996-2005, Valve Corporation, All rights reserved. ======//
 //
 // Purpose: Shared code for parsing / searching for characters in a string
 //			using lookup tables
@@ -15,6 +15,7 @@
 #pragma once
 #endif
 
+#include "platform.h"
 
 struct characterset_t
 {
@@ -28,7 +29,7 @@ struct characterset_t
 // Input  : *pSetBuffer - pointer to the buffer for the group
 //			*pSetString - list of characters to flag
 //-----------------------------------------------------------------------------
-extern void CharacterSetBuild( characterset_t *pSetBuffer, const char *pSetString );
+PLATFORM_INTERFACE void CharacterSetBuild( characterset_t *pSetBuffer, const char *pSetString );
 
 
 //-----------------------------------------------------------------------------
diff --git a/tier1/characterset.cpp b/tier1/characterset.cpp
deleted file mode 100644
index 3914ae0a..00000000
--- a/tier1/characterset.cpp
+++ /dev/null
@@ -1,41 +0,0 @@
-//========= Copyright © 1996-2005, Valve Corporation, All rights reserved. ============//
-//
-// Purpose: 
-//
-// $Workfile:     $
-// $Date:         $
-//
-//-----------------------------------------------------------------------------
-// $Log: $
-//
-// $NoKeywords: $
-//=============================================================================
-
-#include <string.h>
-#include "characterset.h"
-
-// memdbgon must be the last include file in a .cpp file!!!
-#include "tier0/memdbgon.h"
-
-//-----------------------------------------------------------------------------
-// Purpose: builds a simple lookup table of a group of important characters
-// Input  : *pParseGroup - pointer to the buffer for the group
-//			*pGroupString - null terminated list of characters to flag
-//-----------------------------------------------------------------------------
-void CharacterSetBuild( characterset_t *pSetBuffer, const char *pszSetString )
-{
-	int i = 0;
-
-	// Test our pointers
-	if ( !pSetBuffer || !pszSetString )
-		return;
-
-	memset( pSetBuffer->set, 0, sizeof(pSetBuffer->set) );
-
-	while ( pszSetString[i] )
-	{
-		pSetBuffer->set[ static_cast<size_t>(pszSetString[i]) ] = 1;
-		i++;
-	}
-
-}