diff --git a/src/html-minifier.cr b/src/html-minifier.cr
index 2f19671..7474654 100644
--- a/src/html-minifier.cr
+++ b/src/html-minifier.cr
@@ -32,14 +32,16 @@ module HtmlMinifier
     ctx.eval!("var minify = require('html-minifier').minify;")
     ctx
   end
-  @@ctx : Duktape::Sandbox = initialize_context
+  @@ctx : Duktape::Sandbox? = nil
 
   def self.minify!(source : String)
+    @@ctx ||= initialize_context
+    ctx = @@ctx.not_nil!
     source = source.gsub("\"", "\\\"")
     source = source.gsub("\n", "\\n")
     source = source.gsub("'", "\\'")
-    @@ctx.eval!("var output = minify(\'#{source}\', options);")
-    @@ctx.eval!("output")
-    @@ctx.get_string(-1).not_nil!
+    ctx.eval!("var output = minify(\'#{source}\', options);")
+    ctx.eval!("output")
+    ctx.get_string(-1).not_nil!
   end
 end