1 files changed, 3 insertions, 0 deletions
diff --git a/array.c b/array.c
index 5852347584..577953a389 100644
--- a/array.c
+++ b/array.c
@@ -877,6 +877,8 @@ rb_ary_fetch(int argc, VALUE *argv, VALUE ary)
  *     a.index("b")        #=> 1
  *     a.index("z")        #=> nil
  *     a.index{|x|x=="b"}  #=> 1
+ *
+ *  This is an alias of <code>#find_index</code>.
  */
 
 static VALUE
@@ -3378,6 +3380,7 @@ Init_Array(void)
     rb_define_method(rb_cArray, "length", rb_ary_length, 0);
     rb_define_alias(rb_cArray,  "size", "length");
     rb_define_method(rb_cArray, "empty?", rb_ary_empty_p, 0);
+    rb_define_method(rb_cArray, "find_index", rb_ary_index, -1);
     rb_define_method(rb_cArray, "index", rb_ary_index, -1);
     rb_define_method(rb_cArray, "rindex", rb_ary_rindex, -1);
     rb_define_method(rb_cArray, "join", rb_ary_join_m, -1);