diff --git a/tool/mkconfig.rb b/tool/mkconfig.rb
index 07076d491e..e68b288cfd 100755
--- a/tool/mkconfig.rb
+++ b/tool/mkconfig.rb
@@ -42,6 +42,8 @@ v_others = []
 vars = {}
 continued_name = nil
 continued_line = nil
+install_name = nil
+so_name = nil
 File.foreach "config.status" do |line|
   next if /^#/ =~ line
   name = nil
@@ -75,8 +77,8 @@ File.foreach "config.status" do |line|
     when /^(?:X|(?:MINI|RUN|BASE)RUBY$)/; next
     when /^(?:MAJOR|MINOR|TEENY)$/; next
     when /^LIBRUBY_D?LD/; next
-    when /^RUBY_INSTALL_NAME$/; next if $install_name
-    when /^RUBY_SO_NAME$/; next if $so_name
+    when /^RUBY_INSTALL_NAME$/; next vars[name] = (install_name = val).dup if $install_name
+    when /^RUBY_SO_NAME$/; next vars[name] = (so_name = val).dup if $so_name
     when /^arch$/; if val.empty? then val = arch else arch = val end
     when /^sitearch$/; val = '$(arch)' if val.empty?
     end
@@ -215,10 +217,16 @@ end
 v_others.compact!
 
 if $install_name
+  if install_name and vars.expand("$(RUBY_INSTALL_NAME)") == $install_name
+    $install_name = install_name
+  end
   v_fast << "  CONFIG[\"ruby_install_name\"] = \"" + $install_name + "\"\n"
   v_fast << "  CONFIG[\"RUBY_INSTALL_NAME\"] = \"" + $install_name + "\"\n"
 end
 if $so_name
+  if so_name and vars.expand("$(RUBY_SO_NAME)") == $so_name
+    $so_name = so_name
+  end
   v_fast << "  CONFIG[\"RUBY_SO_NAME\"] = \"" + $so_name + "\"\n"
 end