diff -Naur a/configure b/configure
--- a/configure	2019-10-17 17:28:10.000000000 +0300
+++ b/configure	2021-02-19 11:32:45.084523937 +0200
@@ -17652,7 +17652,7 @@
 
 
 tmp_CXXFLAGS="$CXXFLAGS"
-CXXFLAGS="$CXXFLAGS -Wall -Werror -fvisibility=hidden"
+CXXFLAGS="$CXXFLAGS -fvisibility=hidden"
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports the visibility attribute" >&5
 $as_echo_n "checking whether $CC supports the visibility attribute... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
@@ -18413,7 +18413,7 @@
                 if test "x$ax_pthread_try" = "xunknown"; then :
   break
 fi
-                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                CFLAGS="-Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
                 ac_link="$ax_pthread_save_ac_link"
                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
@@ -19102,7 +19102,7 @@
 done
 
 
-CXXFLAGS="$CXXFLAGS -Wall -Werror -pedantic"
+CXXFLAGS="$CXXFLAGS -pedantic"
 
 ac_config_files="$ac_config_files Makefile src/Makefile src/tools/Makefile java/Makefile test/Makefile cs/Makefile cl/Makefile src/libvoikko.pc"