-}], ginac_cv_rlversion=`cat 'conftest.out'`, ginac_cv_rlversion='unknown', ginac_cv_rlversion='4.2')])
+}], [
+dnl Some non-GNU readline implementations have non-numeric rl_library_version
+ginac_cv_rlversion=`sed -e 's/[[^0-9.]]//g' 'conftest.out'`], [ ginac_cv_rlversion='unknown'], [ ginac_cv_rlversion='4.2'])])
+if test -z "$ginac_cv_rlversion"; then
+ GINAC_WARNING([Unsupported version of libreadline.])
+ ginac_cv_rlversion='unknown'
+fi