diff --git a/string.c b/string.c
index 04984f0..f2c46d6 100644
--- a/string.c
+++ b/string.c
@@ -7754,6 +7754,28 @@ rb_str_ellipsize(VALUE str, long len)
 
 /*
  *  call-seq:
+ *     Symbol[str]    => Symbol or nil
+ *
+ *  Returns an extant symbol, which is the .to_sym of +str+, or
+ *  nil if no such symbol exists.
+ *
+ *     Symbol['Object']      #=> :Object
+ *     Symbol['none such']   #=> nil
+ */
+
+VALUE
+sym_lookup(VALUE cls, VALUE str)
+{
+    st_data_t id;
+    if (id = rb_check_id(&str)) {
+	return ID2SYM(id);
+    }
+    return Qnil;
+}
+
+
+/*
+ *  call-seq:
  *     sym == obj   -> true or false
  *
  *  Equality---If <i>sym</i> and <i>obj</i> are exactly the same
@@ -8307,6 +8329,7 @@ Init_String(void)
     rb_undef_alloc_func(rb_cSymbol);
     rb_undef_method(CLASS_OF(rb_cSymbol), "new");
     rb_define_singleton_method(rb_cSymbol, "all_symbols", rb_sym_all_symbols, 0); /* in parse.y */
+    rb_define_singleton_method(rb_cSymbol, "[]", sym_lookup, 1);
 
     rb_define_method(rb_cSymbol, "==", sym_equal, 1);
     rb_define_method(rb_cSymbol, "===", sym_equal, 1);