diff --git a/string.c b/string.c
index a0e413a267..a526d9b712 100644
--- a/string.c
+++ b/string.c
@@ -7024,7 +7024,7 @@ rb_str_chop_bang(VALUE str)
 	long len;
 	len = chopped_length(str);
 	STR_SET_LEN(str, len);
-	RSTRING_PTR(str)[len] = '\0';
+	TERM_FILL(&RSTRING_PTR(str)[len], TERM_LEN(str));
 	if (ENC_CODERANGE(str) != ENC_CODERANGE_7BIT) {
 	    ENC_CODERANGE_CLEAR(str);
 	}
diff --git a/test/-ext-/string/test_cstr.rb b/test/-ext-/string/test_cstr.rb
index a1288373ba..89ab3bb7b0 100644
--- a/test/-ext-/string/test_cstr.rb
+++ b/test/-ext-/string/test_cstr.rb
@@ -52,6 +52,10 @@ class Test_StringCStr < Test::Unit::TestCase
     assert_wchars_term_char("a\n") {|s| s.chop!}
   end
 
+  def test_wchar_chomp!
+    assert_wchars_term_char("a\n") {|s| s.chomp!}
+  end
+
   def assert_wchars_term_char(str)
     result = {}
     WCHARS.map do |enc|