diff --git a/distrib/msw/tmake/vc6base.t b/distrib/msw/tmake/vc6base.t
index c69fed6103..a16aa3580f 100644
--- a/distrib/msw/tmake/vc6base.t
+++ b/distrib/msw/tmake/vc6base.t
@@ -73,8 +73,8 @@ RSC=rc.exe
 # PROP Output_Dir "BaseRelease"
 # PROP Intermediate_Dir "BaseRelease"
 # PROP Target_Dir ""
-# ADD BASE CPP /nologo /MD /W3 /GX /O2 /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /D "_MT" /YX /FD /c
-# ADD CPP /nologo /MD /W4 /Zi /O2 /I "$(wx)\include" /I "$(wx)\src\zlib" /D "NDEBUG" /D wxUSE_GUI=0 /D WIN95=1 /D "__WIN95__" /D "WIN32" /D "_WIN32" /D WINVER=0x400 /D "__WINDOWS__" /D "__WXMSW__" /D "__WIN32__" /D "_MT" /Yu"wx/wxprec.h" /FD /c
+# ADD BASE CPP /nologo /MD /W3 /GX /O1 /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /D "_MT" /YX /FD /c
+# ADD CPP /nologo /MD /W4 /Zi /O1 /I "$(wx)\include" /I "$(wx)\src\zlib" /D "NDEBUG" /D wxUSE_GUI=0 /D WIN95=1 /D "__WIN95__" /D "WIN32" /D "_WIN32" /D WINVER=0x400 /D "__WINDOWS__" /D "__WXMSW__" /D "__WIN32__" /D "_MT" /Yu"wx/wxprec.h" /FD /c
 # ADD BASE RSC /l 0x409
 # ADD RSC /l 0x409
 BSC32=bscmake.exe
diff --git a/distrib/msw/tmake/vc6bdll.t b/distrib/msw/tmake/vc6bdll.t
index ef85135667..ffda2cd74f 100644
--- a/distrib/msw/tmake/vc6bdll.t
+++ b/distrib/msw/tmake/vc6bdll.t
@@ -75,8 +75,8 @@ RSC=rc.exe
 # PROP Intermediate_Dir "BaseDllRelease"
 # PROP Ignore_Export_Lib 0
 # PROP Target_Dir ""
-# ADD BASE CPP /nologo /MT /W3 /GX /O2 /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /D "_MBCS" /D "_USRDLL" /D "WXBASEDLL_EXPORTS" /YX /FD /c
-# ADD CPP /nologo /MT /W4 /O2 /I "$(wx)\include" /I "$(wx)\src\zlib" /D "NDEBUG" /D wxUSE_GUI=0 /D "__WIN95__" /D "WIN32" /D "_WIN32" /D WINVER=0x400 /D "__WINDOWS__" /D "__WIN32__" /D "__WXMSW__" /D "_MT" /D "WXMAKINGDLL" /Yu"wx/wxprec.h" /FD /c
+# ADD BASE CPP /nologo /MT /W3 /GX /O1 /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /D "_MBCS" /D "_USRDLL" /D "WXBASEDLL_EXPORTS" /YX /FD /c
+# ADD CPP /nologo /MT /W4 /O1 /I "$(wx)\include" /I "$(wx)\src\zlib" /D "NDEBUG" /D wxUSE_GUI=0 /D "__WIN95__" /D "WIN32" /D "_WIN32" /D WINVER=0x400 /D "__WINDOWS__" /D "__WIN32__" /D "__WXMSW__" /D "_MT" /D "WXMAKINGDLL" /Yu"wx/wxprec.h" /FD /c
 # ADD BASE MTL /nologo /D "NDEBUG" /mktyplib203 /win32
 # ADD MTL /nologo /D "NDEBUG" /mktyplib203 /win32
 # ADD BASE RSC /l 0x409 /d "NDEBUG"