diff --git a/refinerycms-elasticsearch.gemspec b/refinerycms-elasticsearch.gemspec
index 6577967..159edbb 100644
--- a/refinerycms-elasticsearch.gemspec
+++ b/refinerycms-elasticsearch.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 1.9.3'
 
   # Runtime dependencies
-  s.add_dependency 'refinerycms-core', '~> 3.0.0'
+  s.add_dependency 'refinerycms-core', '>= 3.0', '< 4.1'
   s.add_dependency 'patron'
   s.add_dependency 'elasticsearch'
   s.add_dependency 'hashie'