diff --git a/korundum/rubylib/korundum/configure.in.in b/korundum/rubylib/korundum/configure.in.in
index c1c2ce4c..9bd65993 100644
--- a/korundum/rubylib/korundum/configure.in.in
+++ b/korundum/rubylib/korundum/configure.in.in
@@ -15,7 +15,7 @@ else
       RUBY_CFLAGS=`$PKGCONFIG ruby --cflags`
     fi
     if test -z "$RUBY_VERSION"; then
-      for RUBY_TEST in 2.3 2.2 2.1 2.0 1.9; do
+      for RUBY_TEST in 2.5 2.4 2.3 2.2 2.1 2.0 1.9; do
         RUBY_VERSION=`$PKG_CONFIG ruby-$RUBY_TEST --modversion 2>/dev/null`
         if test -n "$RUBY_VERSION"; then
           RUBY_CFLAGS=`$PKG_CONFIG ruby-$RUBY_TEST --cflags`
diff --git a/qtruby/rubylib/qtruby/configure.in.in b/qtruby/rubylib/qtruby/configure.in.in
index e0147c14..ed1519cb 100644
--- a/qtruby/rubylib/qtruby/configure.in.in
+++ b/qtruby/rubylib/qtruby/configure.in.in
@@ -15,7 +15,7 @@ else
       RUBY_CFLAGS=`$PKGCONFIG ruby --cflags`
     fi
     if test -z "$RUBY_VERSION"; then
-      for RUBY_TEST in 2.3 2.2 2.1 2.0 1.9; do
+      for RUBY_TEST in 2.5 2.4 2.3 2.2 2.1 2.0 1.9; do
         RUBY_VERSION=`$PKG_CONFIG ruby-$RUBY_TEST --modversion 2>/dev/null`
         if test -n "$RUBY_VERSION"; then
           RUBY_CFLAGS=`$PKG_CONFIG ruby-$RUBY_TEST --cflags`