diff --git a/unix/tclConfig.h.in b/unix/tclConfig.h.in
--- unix/tclConfig.h.in
+++ unix/tclConfig.h.in
@@ -462,11 +462,8 @@
 
 /* Add the _LARGEFILE64_SOURCE flag when building */
 #undef _LARGEFILE64_SOURCE
 
-/* Add the _LARGEFILE_SOURCE64 flag when building */
-#undef _LARGEFILE_SOURCE64
-
 /* # needed in sys/socket.h Should OS/390 do the right thing with sockets? */
 #undef _OE_SOCKETS
 
 /* Do we really want to follow the standard? Yes we do! */
diff --git a/unix/tcl.m4 b/unix/tcl.m4
--- unix/tcl.m4
+++ unix/tcl.m4
@@ -2471,9 +2471,8 @@
 #
 #	Might define the following vars:
 #		_ISOC99_SOURCE
 #		_LARGEFILE64_SOURCE
-#		_LARGEFILE_SOURCE64
 #
 #--------------------------------------------------------------------
 
 AC_DEFUN([SC_TCL_EARLY_FLAG],[
@@ -2495,10 +2494,8 @@
     SC_TCL_EARLY_FLAG(_ISOC99_SOURCE,[#include <stdlib.h>],
 	[char *p = (char *)strtoll; char *q = (char *)strtoull;])
     SC_TCL_EARLY_FLAG(_LARGEFILE64_SOURCE,[#include <sys/stat.h>],
 	[struct stat64 buf; int i = stat64("/", &buf);])
-    SC_TCL_EARLY_FLAG(_LARGEFILE_SOURCE64,[#include <sys/stat.h>],
-	[char *p = (char *)open64;])
     if test "x${tcl_flags}" = "x" ; then
 	AC_MSG_RESULT([none])
     else
 	AC_MSG_RESULT([${tcl_flags}])
diff --git a/unix/configure b/unix/configure
--- unix/configure
+++ unix/configure
@@ -9317,113 +9317,8 @@
 
 	tcl_flags="$tcl_flags _LARGEFILE64_SOURCE"
     fi
 
-
-    if test "${tcl_cv_flag__largefile_source64+set}" = set; then
-  echo $ECHO_N "(cached) $ECHO_C" >&6
-else
-  cat >conftest.$ac_ext <<_ACEOF
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-#include <sys/stat.h>
-int
-main ()
-{
-char *p = (char *)open64;
-  ;
-  return 0;
-}
-_ACEOF
-rm -f conftest.$ac_objext
-if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
-  (eval $ac_compile) 2>conftest.er1
-  ac_status=$?
-  grep -v '^ *+' conftest.er1 >conftest.err
-  rm -f conftest.er1
-  cat conftest.err >&5
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } &&
-	 { ac_try='test -z "$ac_c_werror_flag"
-			 || test ! -s conftest.err'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; } &&
-	 { ac_try='test -s conftest.$ac_objext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  tcl_cv_flag__largefile_source64=no
-else
-  echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-cat >conftest.$ac_ext <<_ACEOF
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-#define _LARGEFILE_SOURCE64 1
-#include <sys/stat.h>
-int
-main ()
-{
-char *p = (char *)open64;
-  ;
-  return 0;
-}
-_ACEOF
-rm -f conftest.$ac_objext
-if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
-  (eval $ac_compile) 2>conftest.er1
-  ac_status=$?
-  grep -v '^ *+' conftest.er1 >conftest.err
-  rm -f conftest.er1
-  cat conftest.err >&5
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } &&
-	 { ac_try='test -z "$ac_c_werror_flag"
-			 || test ! -s conftest.err'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; } &&
-	 { ac_try='test -s conftest.$ac_objext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  tcl_cv_flag__largefile_source64=yes
-else
-  echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-tcl_cv_flag__largefile_source64=no
-fi
-rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
-fi
-rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
-fi
-
-    if test "x${tcl_cv_flag__largefile_source64}" = "xyes" ; then
-
-cat >>confdefs.h <<\_ACEOF
-#define _LARGEFILE_SOURCE64 1
-_ACEOF
-
-	tcl_flags="$tcl_flags _LARGEFILE_SOURCE64"
-    fi
-
     if test "x${tcl_flags}" = "x" ; then
 	echo "$as_me:$LINENO: result: none" >&5
 echo "${ECHO_T}none" >&6
     else
