1 files changed, 10 insertions, 0 deletions
diff --git a/ext/-test-/string/set_len.c b/ext/-test-/string/set_len.c
index 219cea404c..049da2cdb5 100644
--- a/ext/-test-/string/set_len.c
+++ b/ext/-test-/string/set_len.c
@@ -7,8 +7,18 @@ bug_str_set_len(VALUE str, VALUE len)
     return str;
 }
 
+static VALUE
+bug_str_append(VALUE str, VALUE addendum)
+{
+    StringValue(addendum);
+    rb_str_modify_expand(str, RSTRING_LEN(addendum));
+    memcpy(RSTRING_END(str), RSTRING_PTR(addendum), RSTRING_LEN(addendum));
+    return str;
+}
+
 void
 Init_string_set_len(VALUE klass)
 {
     rb_define_method(klass, "set_len", bug_str_set_len, 1);
+    rb_define_method(klass, "append", bug_str_append, 1);
 }