diff --git a/jekyll-postfiles.gemspec b/jekyll-postfiles.gemspec
index 114cce3..84e5311 100644
--- a/jekyll-postfiles.gemspec
+++ b/jekyll-postfiles.gemspec
@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 2.3.0"
 
-  spec.add_runtime_dependency "jekyll", "~> 3.6"
+  spec.add_runtime_dependency "jekyll", ">= 3.6", "< 5"
 
   spec.add_development_dependency "bundler", "~> 1.16"
   spec.add_development_dependency "rake", "~> 12.0"