diff --git a/src/string.c b/src/string.c
index b29a298c1..1bd3f6f8f 100644
--- a/src/string.c
+++ b/src/string.c
@@ -3006,6 +3006,7 @@ mrb_str_bytesplice(mrb_state *mrb, mrb_value str)
       mrb_get_args(mrb, "iiS", &idx1, &len1, &replace);
       return str_bytesplice(mrb, str, idx1, len1, replace, 0, RSTRING_LEN(replace));
     }
+    mrb_ensure_string_type(mrb, replace);
     if (mrb_range_beg_len(mrb, range1, &idx1, &len1, RSTRING_LEN(str), FALSE) != MRB_RANGE_OK) break;
     if (mrb_range_beg_len(mrb, range2, &idx2, &len2, RSTRING_LEN(replace), FALSE) != MRB_RANGE_OK) break;
     return str_bytesplice(mrb, str, idx1, len1, replace, idx2, len2);
diff --git a/test/t/string.rb b/test/t/string.rb
index caba51b7c..7dbd5bca8 100644
--- a/test/t/string.rb
+++ b/test/t/string.rb
@@ -948,4 +948,7 @@ assert('String#bytesplice') do
   # idx, len, replace, idx, len (len1<len2)
   a = "0123456789"
   assert_equal "0cd23456789", a.bytesplice(1, 1, b, 2, 2)
+
+  # check the object type to replace
+  assert_raise(TypeError) { "0123456789".bytesplice(1, 1, Object.new) }
 end