diff --git a/ChangeLog b/ChangeLog
index 0d505cfbbe..d5cb49f877 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Oct 19 14:22:49 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* basictest/runner.rb: do not clobber the option by --run-opt with
+	  RUBYOPT.  reported by Allen Hewes <rallenh AT hotmail.com>.
+
 Wed Oct 19 00:09:06 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* addr2line.c (parse_debug_line_cu): boundary checks for
diff --git a/basictest/runner.rb b/basictest/runner.rb
index 0330b6d506..0f398e7acc 100755
--- a/basictest/runner.rb
+++ b/basictest/runner.rb
@@ -17,8 +17,8 @@ $stderr.reopen($stdout)
 error = ''
 
 srcdir = File.expand_path('..', File.dirname(__FILE__))
-if opt = ENV["RUBYOPT"]
-  ENV["RUBYOPT"] = opt + " -W1"
+if env = ENV["RUBYOPT"]
+  ENV["RUBYOPT"] = env + " -W1"
 end
 `#{ruby} #{opt} -W1 #{srcdir}/basictest/test.rb #{ARGV.join(' ')}`.each_line do |line|
   if line =~ /^end of test/