diff --git a/Makefile.in b/Makefile.in
index 1bbdcfdc8..000a769a4 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -97,18 +97,10 @@ URL=@URL@
 # STRTOUL=	strtoul.o
 STRTOUL=@STRTOUL@
 
-# [CHANGEME]
-# If you get crashes around a specific number of clients, and that
-# client load comes close or a little over the system-defined value of
-# FD_SETSIZE, override it here and see what happens. You may override
-# the system FD_SETSIZE by setting the FD_SETSIZE Makefile variable to
-# -DFD_SETSIZE=<some number>.
-FD_SETSIZE=@FD_SETSIZE@
-
 # Where is your openssl binary
 OPENSSLPATH=@OPENSSLPATH@
 
-CFLAGS=-I$(INCLUDEDIR) $(XCFLAGS) $(FD_SETSIZE)
+CFLAGS=-I$(INCLUDEDIR) $(XCFLAGS)
 LDFLAGS=@LDFLAGS_PRIVATELIBS@ @HARDEN_LDFLAGS@
 
 SHELL=/bin/sh
diff --git a/configure b/configure
index c7858e85d..0e05fd6bb 100755
--- a/configure
+++ b/configure
@@ -648,7 +648,6 @@ PCRE2_CFLAGS
 PKG_CONFIG_LIBDIR
 PKG_CONFIG_PATH
 PKG_CONFIG
-FD_SETSIZE
 LDFLAGS_PRIVATELIBS
 PIDFILE
 DOCDIR
@@ -4426,54 +4425,6 @@ CC="$saved_CC"
 CXX="$saved_CXX"
 LD="$saved_LD"
 
-ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fwrong-parameter" >&5
-$as_echo_n "checking whether C compiler accepts -fwrong-parameter... " >&6; }
-if ${ax_cv_check_cflags__Werror___fwrong_parameter+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-
-  ax_check_save_flags=$CFLAGS
-  CFLAGS="$CFLAGS -Werror  -fwrong-parameter"
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-int
-main ()
-{
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ax_cv_check_cflags__Werror___fwrong_parameter=yes
-else
-  ax_cv_check_cflags__Werror___fwrong_parameter=no
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-  CFLAGS=$ax_check_save_flags
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_check_cflags__Werror___fwrong_parameter" >&5
-$as_echo "$ax_cv_check_cflags__Werror___fwrong_parameter" >&6; }
-if test x"$ax_cv_check_cflags__Werror___fwrong_parameter" = xyes; then :
-  CFLAGS="$CFLAGS -fwrong-parameter"
-else
-  :
-fi
-
-  ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
@@ -7754,35 +7705,6 @@ else
 fi
 
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if FD_SETSIZE is large enough to allow $ac_fd file descriptors" >&5
-$as_echo_n "checking if FD_SETSIZE is large enough to allow $ac_fd file descriptors... " >&6; }
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-#include <sys/types.h>
-#include <sys/time.h>
-int main() {
-#if FD_SETSIZE < $ac_fd
-#error FD_SETSIZE is smaller than $ac_fd
-#endif
-exit(0);
-}
-
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-else
-
-# must be passed on the commandline to avoid a ``warning, you redefined something''
-FD_SETSIZE="-DFD_SETSIZE=$ac_fd"
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-
-
 case `uname -s` in
 	*SunOS*|*solaris*)
 
diff --git a/configure.ac b/configure.ac
index 52258dd93..4f18e9f3b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -698,23 +698,6 @@ AC_ARG_ENABLE([asan],
   [ac_cv_asan="no"],
   [ac_cv_asan="yes"])
 
-AC_MSG_CHECKING([if FD_SETSIZE is large enough to allow $ac_fd file descriptors])
-AC_COMPILE_IFELSE([
-#include <sys/types.h>
-#include <sys/time.h>
-int main() {
-#if FD_SETSIZE < $ac_fd
-#error FD_SETSIZE is smaller than $ac_fd
-#endif
-exit(0);
-}
-], AC_MSG_RESULT([yes]), [
-# must be passed on the commandline to avoid a ``warning, you redefined something''
-FD_SETSIZE="-DFD_SETSIZE=$ac_fd"
-AC_MSG_RESULT(no)
-])
-AC_SUBST([FD_SETSIZE])
-
 case `uname -s` in
 	*SunOS*|*solaris*)
 		AC_DEFINE([_SOLARIS], [], [Define if you are compiling unrealircd on Sun's (or Oracle's?) Solaris])