diff --git a/ChangeLog b/ChangeLog
index 75592a2746..8a07f6562a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Mar  9 16:41:44 2016  Koichi Sasada  <ko1@atdot.net>
+
+	* benchmark/driver.rb: fix output messages.
+
+	* benchmark/memory_wrapper.rb: use respond_to? because
+	  member? does not work well.
+
 Wed Mar  9 16:20:25 2016  Koichi Sasada  <ko1@atdot.net>
 
 	* benchmark/driver.rb: support memory usage benchmark.
diff --git a/benchmark/driver.rb b/benchmark/driver.rb
index 52d45e17fa..38c6e045f1 100644
--- a/benchmark/driver.rb
+++ b/benchmark/driver.rb
@@ -219,9 +219,9 @@ class BenchmarkDriver
     if @execs.size > 1
       output
       output({
-        rss:  "Memory consuming ratio (RSS) with the result of `#{@execs[0][1]}' (greater is worse)",
-        peak:  "Memory consuming ratio (peak) with the result of `#{@execs[0][1]}' (greater is worse)",
-        size:  "Memory consuming ratio (size) with the result of `#{@execs[0][1]}' (greater is worse)",
+        real: "Speedup ratio: compare with the result of `#{@execs[0][1]}' (greater is better)"
+        peak: "Memory consuming ratio (peak) with the result of `#{@execs[0][1]}' (greater is better)",
+        size: "Memory consuming ratio (size) with the result of `#{@execs[0][1]}' (greater is better)",
       }[@measure_target])
       output if markdown
       output ["name".ljust(name_width), @execs[1..-1].map.with_index{|(_, v), i| sprintf(strformat, v, width[i])}].join("").rstrip
diff --git a/benchmark/memory_wrapper.rb b/benchmark/memory_wrapper.rb
index f96b6f2341..3f4451a037 100644
--- a/benchmark/memory_wrapper.rb
+++ b/benchmark/memory_wrapper.rb
@@ -7,9 +7,9 @@ open(write_file, 'wb'){|f|
   ms = Memory::Status.new
   case target.to_sym
   when :peak
-    key = ms.member?(:hwm) ? :hwm : :peak
+    key = ms.respond_to?(:hwm) ? :hwm : :peak
   when :size
-    key = ms.member?(:rss) ? :rss : :size
+    key = ms.respond_to?(:rss) ? :rss : :size
   end
 
   f.puts ms[key]