diff --git a/configure.in b/configure.in
index 2fa602b969..d443bba9f3 100644
--- a/configure.in
+++ b/configure.in
@@ -1872,15 +1872,6 @@ dnl problems
 if test "x$wx_largefile" = "xyes"; then
     if test "x$ac_cv_sys_file_offset_bits" = "x64"; then
         WX_LARGEFILE_FLAGS="-D_FILE_OFFSET_BITS=64 -D_LARGE_FILES"
-
-        dnl we get "Large Files (ILP32) not supported in strict ANSI mode."
-        dnl #error from HP standard headers when compiling with g++ without this
-        dnl
-        dnl NB: gcc defines __STDC_EXT__=1 for C code, but not for C++, hence
-        dnl     we do this only for CXXFLAGS and not CPPFLAGS
-        if test "$USE_HPUX" = 1 -a "$GXX" = "yes"; then
-            CXXFLAGS="$CXXFLAGS -D__STDC_EXT__=1"
-        fi
     else
         WX_LARGEFILE_FLAGS="-D_LARGE_FILES"
     fi
diff --git a/include/wx/platform.h b/include/wx/platform.h
index 3841c8c6ba..ee3a9458fa 100644
--- a/include/wx/platform.h
+++ b/include/wx/platform.h
@@ -471,6 +471,14 @@
 #    endif
 #endif
 
+/*
+   We get "Large Files (ILP32) not supported in strict ANSI mode." #error
+   from HP-UX standard headers when compiling with g++ without this:
+ */
+#if defined(__HPUX__) && !defined(__STDC_EXT__)
+#   define __STDC_EXT__ 1
+#endif
+
 /* Force linking against required libraries under Windows CE: */
 #ifdef __WXWINCE__
 #   include "wx/msw/wince/libraries.h"