diff --git a/lib/utils.js b/lib/utils.js
new file mode 100644
index 0000000..ca94a1b
--- /dev/null
+++ b/lib/utils.js
@@ -0,0 +1,11 @@
+const once = (fn) => {
+  let called = false;
+  return (...args) => {
+    if (!called) {
+      called = true;
+      return fn(...args);
+    }
+  };
+};
+
+module.exports = { once }
diff --git a/sign.js b/sign.js
index 1aeeabc..d552cfd 100644
--- a/sign.js
+++ b/sign.js
@@ -1,8 +1,9 @@
 const timespan = require('./lib/timespan');
 const PS_SUPPORTED = require('./lib/psSupported');
 const validateAsymmetricKey = require('./lib/validateAsymmetricKey');
+const { once } = require('./lib/utils');
 const jws = require('jws');
-const {includes, isBoolean, isInteger, isNumber, isPlainObject, isString, once} = require('lodash')
+const {includes, isBoolean, isInteger, isNumber, isPlainObject, isString} = require('lodash')
 const { KeyObject, createSecretKey, createPrivateKey } = require('crypto')
 
 const SUPPORTED_ALGS = ['RS256', 'RS384', 'RS512', 'ES256', 'ES384', 'ES512', 'HS256', 'HS384', 'HS512', 'none'];