diff --git a/lib/searchkick/index.rb b/lib/searchkick/index.rb
index d783647..d7f51fb 100644
--- a/lib/searchkick/index.rb
+++ b/lib/searchkick/index.rb
@@ -102,7 +102,11 @@ module Searchkick
     def all_indices(unaliased: false)
       indices =
         begin
-          client.indices.get_aliases
+          if client.indices.respond_to?(:get_alias)
+            client.indices.get_alias
+          else
+            client.indices.get_aliases
+          end
         rescue Elasticsearch::Transport::Transport::Errors::NotFound
           {}
         end
diff --git a/searchkick.gemspec b/searchkick.gemspec
index 1936690..dec6ed4 100644
--- a/searchkick.gemspec
+++ b/searchkick.gemspec
@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = ">= 2.2"
 
   spec.add_dependency "activemodel", ">= 4.2"
-  spec.add_dependency "elasticsearch", ">= 5", "< 6.3"
+  spec.add_dependency "elasticsearch", ">= 5"
   spec.add_dependency "hashie"
 
   spec.add_development_dependency "bundler"
--
libgit2 0.21.0