diff --git a/sim/rx/ChangeLog b/sim/rx/ChangeLog
index b3d76be02d..c92e41cd94 100644
--- a/sim/rx/ChangeLog
+++ b/sim/rx/ChangeLog
@@ -1,3 +1,8 @@
+2021-02-08  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* configure: Regenerate.
+	* configure.ac (SIM_AC_OPTION_WARNINGS): Delete call.
+
 2021-02-08  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* mem.c (mem_put_blk): Rename parameter, add cast from parameter
diff --git a/sim/rx/configure b/sim/rx/configure
index 7e2ac7b948..1781df8a02 100755
--- a/sim/rx/configure
+++ b/sim/rx/configure
@@ -13603,6 +13603,9 @@ if test "${GCC}" = yes -a -z "${ERROR_ON_WARNING}" ; then
 fi
 
 WERROR_CFLAGS=""
+  if test "${ERROR_ON_WARNING}" = yes ; then
+    WERROR_CFLAGS="-Werror"
+  fi
 
 build_warnings="-Wall -Wdeclaration-after-statement -Wpointer-arith \
 -Wpointer-sign \
diff --git a/sim/rx/configure.ac b/sim/rx/configure.ac
index 6c14434f4a..1bdb5abc27 100644
--- a/sim/rx/configure.ac
+++ b/sim/rx/configure.ac
@@ -22,7 +22,6 @@ AC_INIT(Makefile.in)
 sinclude(../common/acinclude.m4)
 
 SIM_AC_COMMON
-SIM_AC_OPTION_WARNINGS(no)
 
 AC_CHECK_HEADERS(getopt.h)