diff --git a/lib/irb/cmd/measure.rb b/lib/irb/cmd/measure.rb
index 244879c10470ec..0806f84ed737c2 100644
--- a/lib/irb/cmd/measure.rb
+++ b/lib/irb/cmd/measure.rb
@@ -14,8 +14,8 @@ def execute(type = nil, arg = nil)
           IRB.conf[:MEASURE] = nil
           IRB.unset_measure_callback(arg)
         when :list
-          IRB.conf[:MEASURE_CALLBACKS].each do |type_name, _, arg|
-            puts "- #{type_name}" + (arg ? "(#{arg.inspect})" : '')
+          IRB.conf[:MEASURE_CALLBACKS].each do |type_name, _, arg_val|
+            puts "- #{type_name}" + (arg_val ? "(#{arg_val.inspect})" : '')
           end
         when :on
           IRB.conf[:MEASURE] = true