diff --git a/declarations/util/memorize.d.ts b/declarations/util/memorize.d.ts
new file mode 100644
index 0000000..5c9968f
--- /dev/null
+++ b/declarations/util/memorize.d.ts
@@ -0,0 +1,7 @@
+export default memoize;
+/**
+ * @template T
+ * @param fn {(function(): any) | undefined}
+ * @returns {function(): T}
+ */
+declare function memoize<T>(fn: (() => any) | undefined): () => T;
diff --git a/src/ValidationError.js b/src/ValidationError.js
index bc026b8..cec8556 100644
--- a/src/ValidationError.js
+++ b/src/ValidationError.js
@@ -1,4 +1,4 @@
-const { stringHints, numberHints } = require("./util/hints");
+import memoize from "./util/memorize";
 
 /** @typedef {import("json-schema").JSONSchema6} JSONSchema6 */
 /** @typedef {import("json-schema").JSONSchema7} JSONSchema7 */
@@ -384,6 +384,11 @@ function formatHints(hints) {
   return hints.length > 0 ? `(${hints.join(", ")})` : "";
 }
 
+const getUtilHints = memoize(() =>
+  // eslint-disable-next-line global-require
+  require("./util/hints")
+);
+
 /**
  * @param {Schema} schema
  * @param {boolean} logic
@@ -391,9 +396,13 @@ function formatHints(hints) {
  */
 function getHints(schema, logic) {
   if (likeNumber(schema) || likeInteger(schema)) {
-    return numberHints(schema, logic);
+    const util = getUtilHints();
+
+    return util.numberHints(schema, logic);
   } else if (likeString(schema)) {
-    return stringHints(schema, logic);
+    const util = getUtilHints();
+
+    return util.stringHints(schema, logic);
   }
 
   return [];
diff --git a/src/util/memorize.js b/src/util/memorize.js
new file mode 100644
index 0000000..414185e
--- /dev/null
+++ b/src/util/memorize.js
@@ -0,0 +1,26 @@
+/**
+ * @template T
+ * @param fn {(function(): any) | undefined}
+ * @returns {function(): T}
+ */
+const memoize = (fn) => {
+  let cache = false;
+  /** @type {T} */
+  let result;
+
+  return () => {
+    if (cache) {
+      return result;
+    }
+    result = /** @type {function(): any} */ (fn)();
+    cache = true;
+    // Allow to clean up memory for fn
+    // and all dependent resources
+    // eslint-disable-next-line no-undefined, no-param-reassign
+    fn = undefined;
+
+    return result;
+  };
+};
+
+export default memoize;
diff --git a/src/validate.js b/src/validate.js
index a072407..a361ecc 100644
--- a/src/validate.js
+++ b/src/validate.js
@@ -1,32 +1,5 @@
-import addAbsolutePathKeyword from "./keywords/absolutePath";
-import addUndefinedAsNullKeyword from "./keywords/undefinedAsNull";
-
 import ValidationError from "./ValidationError";
-
-/**
- * @template T
- * @param fn {(function(): any) | undefined}
- * @returns {function(): T}
- */
-const memoize = (fn) => {
-  let cache = false;
-  /** @type {T} */
-  let result;
-
-  return () => {
-    if (cache) {
-      return result;
-    }
-    result = /** @type {function(): any} */ (fn)();
-    cache = true;
-    // Allow to clean up memory for fn
-    // and all dependent resources
-    // eslint-disable-next-line no-undefined, no-param-reassign
-    fn = undefined;
-
-    return result;
-  };
-};
+import memoize from "./util/memorize";
 
 const getAjv = memoize(() => {
   // Use CommonJS require for ajv libs so TypeScript consumers aren't locked into esModuleInterop (see #110).
@@ -51,7 +24,15 @@ const getAjv = memoize(() => {
   addFormats(ajv, { keywords: true });
 
   // Custom keywords
+  // eslint-disable-next-line global-require
+  const addAbsolutePathKeyword = require("./keywords/absolutePath").default;
+
   addAbsolutePathKeyword(ajv);
+
+  const addUndefinedAsNullKeyword =
+    // eslint-disable-next-line global-require
+    require("./keywords/undefinedAsNull").default;
+
   addUndefinedAsNullKeyword(ajv);
 
   return ajv;