diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3ae8742..75fb764 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 - Added `queue_name` option
 - No longer require synonyms to be lowercase
+- Fixed error with `similar` method and `_all` field
 
 ## 2.2.1
 
diff --git a/lib/searchkick/query.rb b/lib/searchkick/query.rb
index 480774f..7a2a39f 100644
--- a/lib/searchkick/query.rb
+++ b/lib/searchkick/query.rb
@@ -223,13 +223,15 @@ module Searchkick
         if options[:similar]
           payload = {
             more_like_this: {
-              fields: fields,
               like_text: term,
               min_doc_freq: 1,
               min_term_freq: 1,
               analyzer: "searchkick_search2"
             }
           }
+          if fields != ["_all"]
+            payload[:more_like_this][:fields] = fields
+          end
         elsif all
           payload = {
             match_all: {}
--
libgit2 0.21.0