diff --git a/ChangeLog b/ChangeLog
index a717e02..f4277c9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-19  Ben Elliston  <bje@gnu.org>
+
+	* configure.ac: Require Tcl version 8.5 at a minimum.
+	* configure: Regenerate.
+
 2016-02-18  Ben Elliston  <bje@gnu.org>
 
 	* configure.ac: Require Tcl version 8.6 at a minimum.
diff --git a/configure b/configure
index be96384..4465150 100755
--- a/configure
+++ b/configure
@@ -4189,14 +4189,14 @@ if test -z $ac_cv_path_EXPECT ; then
    as_fn_error $? "unable to locate expect" "$LINENO" 5
 fi
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking Tcl version 8.6 or greater" >&5
-$as_echo_n "checking Tcl version 8.6 or greater... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking Tcl version 8.5 or greater" >&5
+$as_echo_n "checking Tcl version 8.5 or greater... " >&6; }
 if ${ac_cv_dg_tcl_modern+:} false; then :
   $as_echo_n "(cached) " >&6
 else
 
   ac_cv_dg_tcl_modern=`$EXPECT << EOF
-if [ expr \\${tcl_version} >= 8.6  ] then { puts yes } else { puts no }
+if [ expr \\${tcl_version} >= 8.5 ] then { puts yes } else { puts no }
 EOF`
 
 fi
@@ -4205,7 +4205,7 @@ if test x${ac_cv_dg_tcl_modern} = xyes ; then
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: ${ac_cv_dg_tcl_modern}" >&5
 $as_echo "${ac_cv_dg_tcl_modern}" >&6; }
 else
-  as_fn_error $? "Tcl 8.6 or greater is required" "$LINENO" 5
+  as_fn_error $? "Tcl 8.5 or greater is required" "$LINENO" 5
 fi
 
 if test x"$DEJAGNU" = x
diff --git a/configure.ac b/configure.ac
index e51aa9a..c1057c5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,17 +43,17 @@ if test -z $ac_cv_path_EXPECT ; then
    AC_MSG_ERROR([unable to locate expect])
 fi
 
-dnl Check the Tcl version is >= 8.6.
-AC_MSG_CHECKING([Tcl version 8.6 or greater])
+dnl Check the Tcl version is >= 8.5.
+AC_MSG_CHECKING([Tcl version 8.5 or greater])
 AC_CACHE_VAL(ac_cv_dg_tcl_modern,[
   ac_cv_dg_tcl_modern=`$EXPECT << EOF
-if @<:@ expr \\${tcl_version} >= 8.6  @:>@ then { puts yes } else { puts no }
+if @<:@ expr \\${tcl_version} >= 8.5 @:>@ then { puts yes } else { puts no }
 EOF`
 ])
 if test x${ac_cv_dg_tcl_modern} = xyes ; then
   AC_MSG_RESULT(${ac_cv_dg_tcl_modern})
 else
-  AC_MSG_ERROR([Tcl 8.6 or greater is required])
+  AC_MSG_ERROR([Tcl 8.5 or greater is required])
 fi
 
 if test x"$DEJAGNU" = x