diff --git a/configure b/configure
index 569cd2fa91..9625a82f0d 100755
--- a/configure
+++ b/configure
@@ -15169,30 +15169,9 @@ _ACEOF
 
 fi
 
-ac_fn_c_check_func "$LINENO" "fseeko" "ac_cv_func_fseeko"
-if test "x$ac_cv_func_fseeko" = xyes; then :
-  $as_echo "#define HAVE_FSEEKO 1" >>confdefs.h
-
-else
-  case " $LIBOBJS " in
-  *" fseeko.$ac_objext "* ) ;;
-  *) LIBOBJS="$LIBOBJS fseeko.$ac_objext"
- ;;
-esac
-
-fi
-
-
-case $host_os in
-	# NetBSD uses a custom fseeko/ftello built on fsetpos/fgetpos
-	# Mingw uses macros to access Win32 API calls
-	netbsd*|mingw*)
-
-$as_echo "#define HAVE_FSEEKO 1" >>confdefs.h
-
-		ac_cv_func_fseeko=yes;;
-	*)
-		{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for _LARGEFILE_SOURCE value needed for large files" >&5
+# We require 64-bit fseeko() to be available, but run this check anyway
+# in case it finds that _LARGEFILE_SOURCE has to be #define'd for that.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for _LARGEFILE_SOURCE value needed for large files" >&5
 $as_echo_n "checking for _LARGEFILE_SOURCE value needed for large files... " >&6; }
 if ${ac_cv_sys_largefile_source+:} false; then :
   $as_echo_n "(cached) " >&6
@@ -15259,8 +15238,7 @@ if test $ac_cv_sys_largefile_source != unknown; then
 $as_echo "#define HAVE_FSEEKO 1" >>confdefs.h
 
 fi
-;;
-esac
+
 
 # posix_fadvise() is a no-op on Solaris, so don't incur function overhead
 # by calling it, 2009-04-02
diff --git a/configure.in b/configure.in
index 140909091a..a70870184f 100644
--- a/configure.in
+++ b/configure.in
@@ -1660,16 +1660,9 @@ PGAC_CHECK_BUILTIN_FUNC([__builtin_clz], [unsigned int x])
 PGAC_CHECK_BUILTIN_FUNC([__builtin_ctz], [unsigned int x])
 PGAC_CHECK_BUILTIN_FUNC([__builtin_popcount], [unsigned int x])
 
-AC_REPLACE_FUNCS(fseeko)
-case $host_os in
-	# NetBSD uses a custom fseeko/ftello built on fsetpos/fgetpos
-	# Mingw uses macros to access Win32 API calls
-	netbsd*|mingw*)
-		AC_DEFINE(HAVE_FSEEKO, 1, [Define to 1 because replacement version used.])
-		ac_cv_func_fseeko=yes;;
-	*)
-		AC_FUNC_FSEEKO;;
-esac
+# We require 64-bit fseeko() to be available, but run this check anyway
+# in case it finds that _LARGEFILE_SOURCE has to be #define'd for that.
+AC_FUNC_FSEEKO
 
 # posix_fadvise() is a no-op on Solaris, so don't incur function overhead
 # by calling it, 2009-04-02
diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c
index 77bf9edaba..15900ffc24 100644
--- a/src/bin/pg_dump/pg_backup_archiver.c
+++ b/src/bin/pg_dump/pg_backup_archiver.c
@@ -3872,15 +3872,6 @@ checkSeek(FILE *fp)
 {
 	pgoff_t		tpos;
 
-	/*
-	 * If pgoff_t is wider than long, we must have "real" fseeko and not an
-	 * emulation using fseek.  Otherwise report no seek capability.
-	 */
-#ifndef HAVE_FSEEKO
-	if (sizeof(pgoff_t) > sizeof(long))
-		return false;
-#endif
-
 	/* Check that ftello works on this file */
 	tpos = ftello(fp);
 	if (tpos < 0)
diff --git a/src/include/port.h b/src/include/port.h
index 2767cf0fc3..3f5f90fa00 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -331,13 +331,9 @@ extern int	gettimeofday(struct timeval *tp, struct timezone *tzp);
  * When necessary, these routines are provided by files in src/port/.
  */
 
-/* WIN32 handled in port/win32_port.h */
-#ifndef WIN32
+/* Type to use with fseeko/ftello */
+#ifndef WIN32					/* WIN32 is handled in port/win32_port.h */
 #define pgoff_t off_t
-#ifdef __NetBSD__
-extern int	fseeko(FILE *stream, off_t offset, int whence);
-extern off_t ftello(FILE *stream);
-#endif
 #endif
 
 extern double pg_erand48(unsigned short xseed[3]);
@@ -349,11 +345,6 @@ extern void pg_srand48(long seed);
 extern int	fls(int mask);
 #endif
 
-#ifndef HAVE_FSEEKO
-#define fseeko(a, b, c) fseek(a, b, c)
-#define ftello(a)		ftell(a)
-#endif
-
 #ifndef HAVE_GETPEEREID
 /* On Windows, Perl might have incompatible definitions of uid_t and gid_t. */
 #ifndef PLPERL_HAVE_UID_GID
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index ec0e3d5a37..91ec01468e 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -193,6 +193,7 @@ int			setitimer(int which, const struct itimerval *value, struct itimerval *oval
  * with 64-bit offsets.
  */
 #define pgoff_t __int64
+
 #ifdef _MSC_VER
 #define fseeko(stream, offset, origin) _fseeki64(stream, offset, origin)
 #define ftello(stream) _ftelli64(stream)
diff --git a/src/port/fseeko.c b/src/port/fseeko.c
deleted file mode 100644
index 02c1bcd251..0000000000
--- a/src/port/fseeko.c
+++ /dev/null
@@ -1,84 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * fseeko.c
- *	  64-bit versions of fseeko/ftello()
- *
- * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- *	  src/port/fseeko.c
- *
- *-------------------------------------------------------------------------
- */
-
-/*
- * We have to use the native defines here because configure hasn't
- * completed yet.
- */
-#ifdef __NetBSD__
-
-#include "c.h"
-
-#include <sys/stat.h>
-
-
-/*
- *	On NetBSD, off_t and fpos_t are the same.  Standards
- *	say off_t is an arithmetic type, but not necessarily integral,
- *	while fpos_t might be neither.
- */
-
-int
-fseeko(FILE *stream, off_t offset, int whence)
-{
-	off_t		floc;
-	struct stat filestat;
-
-	switch (whence)
-	{
-		case SEEK_CUR:
-			if (fgetpos(stream, &floc) != 0)
-				goto failure;
-			floc += offset;
-			if (fsetpos(stream, &floc) != 0)
-				goto failure;
-			return 0;
-			break;
-		case SEEK_SET:
-			if (fsetpos(stream, &offset) != 0)
-				return -1;
-			return 0;
-			break;
-		case SEEK_END:
-			fflush(stream);		/* force writes to fd for stat() */
-			if (fstat(fileno(stream), &filestat) != 0)
-				goto failure;
-			floc = filestat.st_size;
-			floc += offset;
-			if (fsetpos(stream, &floc) != 0)
-				goto failure;
-			return 0;
-			break;
-		default:
-			errno = EINVAL;
-			return -1;
-	}
-
-failure:
-	return -1;
-}
-
-
-off_t
-ftello(FILE *stream)
-{
-	off_t		floc;
-
-	if (fgetpos(stream, &floc) != 0)
-		return -1;
-	return floc;
-}
-
-#endif
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index a43e31c60e..6a1435f456 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -94,7 +94,7 @@ sub mkvcbuild
 	$solution = CreateSolution($vsVersion, $config);
 
 	our @pgportfiles = qw(
-	  chklocale.c explicit_bzero.c fls.c fseeko.c getpeereid.c getrusage.c inet_aton.c random.c
+	  chklocale.c explicit_bzero.c fls.c getpeereid.c getrusage.c inet_aton.c random.c
 	  srandom.c getaddrinfo.c gettimeofday.c inet_net_ntop.c kill.c open.c
 	  erand48.c snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c
 	  dirent.c dlopen.c getopt.c getopt_long.c