diff --git a/lib/jwk/key/base.js b/lib/jwk/key/base.js
index bfad0126..15b8c817 100644
--- a/lib/jwk/key/base.js
+++ b/lib/jwk/key/base.js
@@ -57,6 +57,9 @@ class Key {
         throw new TypeError('`x5c` must be an array of one or more PKIX certificates when provided')
       }
 
+      x5c = [...x5c]
+      Object.freeze(x5c)
+
       x5c.forEach((cert, i) => {
         let publicKey
         try {