diff --git a/Gemfile b/Gemfile
index 78a22e4e954..9842fe8c0fe 100644
--- a/Gemfile
+++ b/Gemfile
@@ -19,7 +19,7 @@ gem 'rubocop', group: :test
 
 # All of this is for Slate / middleman
 
-gem "middleman", '~> 3.0'
+gem "middleman", "~> 4.0", ">= 4.0.0"
 
 # For syntax highlighting
 gem "middleman-syntax"