diff --git a/common/GameUI/IGameConsole.h b/common/GameUI/IGameConsole.h
index ffbbbffe..33884692 100644
--- a/common/GameUI/IGameConsole.h
+++ b/common/GameUI/IGameConsole.h
@@ -10,7 +10,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 
 
 //-----------------------------------------------------------------------------
diff --git a/public/appframework/IAppSystemGroup.h b/public/appframework/IAppSystemGroup.h
index b5cad8ba..f181b9d0 100644
--- a/public/appframework/IAppSystemGroup.h
+++ b/public/appframework/IAppSystemGroup.h
@@ -20,7 +20,7 @@
 #endif
 
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/utlvector.h"
 #include "tier1/utldict.h"
 #include "tier1/UtlStringMap.h"
diff --git a/public/bitmap/tgawriter.h b/public/bitmap/tgawriter.h
index c9c24493..7d2c8ef2 100644
--- a/public/bitmap/tgawriter.h
+++ b/public/bitmap/tgawriter.h
@@ -12,7 +12,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "bitmap/imageformat.h" //ImageFormat enum definition
 
 class CUtlBuffer;
diff --git a/public/datamodel/idatamodel.h b/public/datamodel/idatamodel.h
index 4655d073..37d0eac3 100644
--- a/public/datamodel/idatamodel.h
+++ b/public/datamodel/idatamodel.h
@@ -10,7 +10,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/utlvector.h"
 #include "tier1/utlsymbollarge.h"
 #include "appframework/IAppSystem.h"
diff --git a/public/engine/ishadowmgr.h b/public/engine/ishadowmgr.h
index 154df68e..f5bc62c3 100644
--- a/public/engine/ishadowmgr.h
+++ b/public/engine/ishadowmgr.h
@@ -13,7 +13,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "mathlib/vmatrix.h"
 
 
diff --git a/public/istudiorender.h b/public/istudiorender.h
index 916881a6..a7d6d89d 100644
--- a/public/istudiorender.h
+++ b/public/istudiorender.h
@@ -11,7 +11,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "mathlib/vector.h"
 #include "mathlib/vector4d.h"
 #include "tier1/utlbuffer.h"
diff --git a/public/ivtex.h b/public/ivtex.h
index ddccd1a4..008bda9f 100644
--- a/public/ivtex.h
+++ b/public/ivtex.h
@@ -12,7 +12,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 
 
 class IVTex
diff --git a/public/matchmaking/imatchframework.h b/public/matchmaking/imatchframework.h
index 808e9919..8adbe64d 100644
--- a/public/matchmaking/imatchframework.h
+++ b/public/matchmaking/imatchframework.h
@@ -17,7 +17,7 @@ class IMatchSession;
 
 #include "appframework/iAppSystem.h"
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "keyvalues.h"
 
 #if !defined( _X360 )
diff --git a/public/materialsystem/IColorCorrection.h b/public/materialsystem/IColorCorrection.h
index c3cc07c5..902e2ea3 100644
--- a/public/materialsystem/IColorCorrection.h
+++ b/public/materialsystem/IColorCorrection.h
@@ -11,7 +11,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier0/basetypes.h"
 #include "bitmap/imageformat.h"
 
diff --git a/public/materialsystem/imaterialsystem.h b/public/materialsystem/imaterialsystem.h
index 61d3201b..d74e3fb8 100644
--- a/public/materialsystem/imaterialsystem.h
+++ b/public/materialsystem/imaterialsystem.h
@@ -18,7 +18,7 @@
 #define GAMMA 2.2f
 #define TEXGAMMA 2.2f
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/refcount.h"
 #include "mathlib/vector.h"
 #include "mathlib/vector4d.h"
diff --git a/public/materialsystem/imaterialsystemhardwareconfig.h b/public/materialsystem/imaterialsystemhardwareconfig.h
index 50b51742..13ab4217 100644
--- a/public/materialsystem/imaterialsystemhardwareconfig.h
+++ b/public/materialsystem/imaterialsystemhardwareconfig.h
@@ -14,7 +14,7 @@
 #endif
 
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier2/tier2.h"
 
 #include "bitmap/imageformat.h"
diff --git a/public/materialsystem/imesh.h b/public/materialsystem/imesh.h
index 16fce7b1..40ae062c 100644
--- a/public/materialsystem/imesh.h
+++ b/public/materialsystem/imesh.h
@@ -11,7 +11,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "materialsystem/imaterial.h"
 #include <float.h>
 #include <string.h>
diff --git a/public/matsys_controls/matsyscontrols.h b/public/matsys_controls/matsyscontrols.h
index 271a6579..27e31e6c 100644
--- a/public/matsys_controls/matsyscontrols.h
+++ b/public/matsys_controls/matsyscontrols.h
@@ -12,7 +12,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 
 
 //-----------------------------------------------------------------------------
diff --git a/public/maya/valveMaya.h b/public/maya/valveMaya.h
index 5c610cc1..ac6a53ae 100644
--- a/public/maya/valveMaya.h
+++ b/public/maya/valveMaya.h
@@ -33,7 +33,7 @@
 #include "tier1/utlstring.h"
 #include "tier1/utlstringmap.h"
 #include "tier1/utlvector.h"
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "mathlib/mathlib.h"
 
 #include "ValveMaya/Undo.h"
diff --git a/public/shaderapi/IShaderDevice.h b/public/shaderapi/IShaderDevice.h
index 5b153488..f40f42e6 100644
--- a/public/shaderapi/IShaderDevice.h
+++ b/public/shaderapi/IShaderDevice.h
@@ -13,7 +13,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "appframework/IAppSystem.h"
 #include "bitmap/imageformat.h"
 #include "tier1/utlbuffer.h"
diff --git a/public/toolframework/itoolentity.h b/public/toolframework/itoolentity.h
index 205dce6e..b8ff1ff9 100644
--- a/public/toolframework/itoolentity.h
+++ b/public/toolframework/itoolentity.h
@@ -10,7 +10,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/utlvector.h"
 #include "Color.h"
 #include "basehandle.h"
diff --git a/public/vgui/IInput.h b/public/vgui/IInput.h
index bd45952f..47090775 100644
--- a/public/vgui/IInput.h
+++ b/public/vgui/IInput.h
@@ -13,7 +13,7 @@
 #endif
 
 #include <vgui/VGUI.h>
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "vgui/MouseCode.h"
 #include "vgui/KeyCode.h"
 
diff --git a/public/vgui/IPanel.h b/public/vgui/IPanel.h
index 6fe1dff8..19291617 100644
--- a/public/vgui/IPanel.h
+++ b/public/vgui/IPanel.h
@@ -13,7 +13,7 @@
 #endif
 
 #include <vgui/VGUI.h>
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/utlvector.h"
 
 #ifdef SendMessage
diff --git a/public/vgui/IScheme.h b/public/vgui/IScheme.h
index c0e38549..d4fdf86d 100644
--- a/public/vgui/IScheme.h
+++ b/public/vgui/IScheme.h
@@ -13,7 +13,7 @@
 #endif
 
 #include "vgui/vgui.h"
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/utlsymbol.h"
 
 class Color;
diff --git a/public/vgui/ISurface.h b/public/vgui/ISurface.h
index 7256b461..8005d0b9 100644
--- a/public/vgui/ISurface.h
+++ b/public/vgui/ISurface.h
@@ -14,7 +14,7 @@
 
 #include "vgui/VGUI.h"
 #include "vgui/IHTML.h" // CreateHTML, PaintHTML 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "bitmap/imageformat.h"
 
 #include "appframework/IAppSystem.h"
diff --git a/public/vgui/ISystem.h b/public/vgui/ISystem.h
index c31b1ccb..9ef6e44a 100644
--- a/public/vgui/ISystem.h
+++ b/public/vgui/ISystem.h
@@ -12,7 +12,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "tier1/keyvalues.h"
 #include <vgui/VGUI.h>
 #include <vgui/KeyCode.h>
diff --git a/public/vgui/IVGui.h b/public/vgui/IVGui.h
index 52b0b870..f2ea9245 100644
--- a/public/vgui/IVGui.h
+++ b/public/vgui/IVGui.h
@@ -12,7 +12,7 @@
 #pragma once
 #endif
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include <vgui/VGUI.h>
 
 #include "appframework/IAppSystem.h"
diff --git a/public/vgui_controls/Controls.h b/public/vgui_controls/Controls.h
index 26397d08..090e70a9 100644
--- a/public/vgui_controls/Controls.h
+++ b/public/vgui_controls/Controls.h
@@ -16,7 +16,7 @@
 #include <vgui/IPanel.h>
 #include <vstdlib/IKeyValuesSystem.h>
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "vgui/MouseCode.h"
 #include "vgui/KeyCode.h"
 #include "tier3/tier3.h"
diff --git a/public/vphysics_interface.h b/public/vphysics_interface.h
index d9e4eff3..f36371be 100644
--- a/public/vphysics_interface.h
+++ b/public/vphysics_interface.h
@@ -12,7 +12,7 @@
 #endif
 
 
-#include "tier1/interface.h"
+#include "tier0/interface.h"
 #include "appframework/IAppSystem.h"
 #include "mathlib/vector.h"
 #include "mathlib/vector4d.h"