diff --git a/packages/ctl/ctl.js b/packages/ctl/ctl.js
index a699e22f..07c16fbc 100755
--- a/packages/ctl/ctl.js
+++ b/packages/ctl/ctl.js
@@ -10,6 +10,8 @@ const yargs = require("yargs");
 const version = require("./package").version;
 const setBlocking = require("set-blocking");
 
+// Reduce startup time by lazy compiling schemas.
+global.lazySchemaCompilation = true;
 const lib = require("@clusterio/lib");
 const { ConsoleTransport, levels, logger } = lib;
 
diff --git a/packages/lib/src/schema.js b/packages/lib/src/schema.js
index 65f90937..63c2f5c9 100644
--- a/packages/lib/src/schema.js
+++ b/packages/lib/src/schema.js
@@ -5,18 +5,36 @@
 "use strict";
 const Ajv = require("ajv");
 const ajv = new Ajv({
+	// These are duplicated in scripts/compile_validator
 	allowUnionTypes: true,
 	strict: "log",
 	strictTuples: false,
 	verbose: true,
 });
 
+/**
+ * Compile JSON schema into validator
+ * @function
+ * @param {Object} schema - JSON schema to create validator for.
+ * @returns {Function} Validator for the schema.
+ */
+function compile(schema) {
+	if (typeof global !== "object" || !global.lazySchemaCompilation) {
+		return ajv.compile(schema);
+	}
+
+	let doValidate;
+	function validate(data) {
+		if (!doValidate) {
+			doValidate = ajv.compile(schema);
+		}
+		let result = doValidate(data);
+		validate.errors = doValidate.errors;
+		return result;
+	}
+	return validate;
+}
+
 module.exports = {
-	/**
-	 * Compile JSON schema into validator
-	 * @function
-	 * @param {Object} schema - JSON schema to create validator for.
-	 * @returns {Function} Validator for the schema.
-	 */
-	compile: ajv.compile.bind(ajv),
+	compile,
 };