diff --git a/ChangeLog b/ChangeLog
index 73371bc898..d1bf010e8d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Jan 29 14:13:28 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/erb.rb (ERB#def_method): insert def line just before the
+	  first non-comment and non-empty line, not to leave duplicated
+	  and stale magic comments.
+
 Fri Jan 29 11:13:33 2016  Jeremy Evans  <code@jeremyevans.net>
 
 	* lib/erb.rb (ERB#set_eoutvar): explicitly make mutable string as
diff --git a/lib/erb.rb b/lib/erb.rb
index 2e9fad98b4..7c22ec2efa 100644
--- a/lib/erb.rb
+++ b/lib/erb.rb
@@ -905,10 +905,9 @@ class ERB
   #   erb.def_method(MyClass, 'render(arg1, arg2)', filename)
   #   print MyClass.new.render('foo', 123)
   def def_method(mod, methodname, fname='(ERB)')
-    src = self.src
-    magic_comment = "#coding:#{@encoding}\n"
+    src = self.src.sub(/^(?!#|$)/) {"def #{methodname}\n"} << "\nend\n"
     mod.module_eval do
-      eval(magic_comment + "def #{methodname}\n" + src + "\nend\n", binding, fname, -2)
+      eval(src, binding, fname, -1)
     end
   end