diff --git a/src/lib.rs b/src/lib.rs
index 4a4b805..cb3750c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -104,7 +104,7 @@ pub struct X509Params {
 
     /// x5c: The certificate chain used to verify this key.
     #[serde(default, rename = "x5c", skip_serializing_if = "Option::is_none")]
-    cert_chain: Option<String>,
+    cert_chain: Option<Vec<String>>,
 
     /// x5t: The SHA-1 thumbprint of the DER-encoded X.509 version of the public key.
     #[serde(default, rename = "x5t", skip_serializing_if = "Option::is_none")]
diff --git a/src/tests.rs b/src/tests.rs
index bdf74db..52190af 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -430,7 +430,7 @@ fn x509_params() {
         "kty": "oct",
         "k": "TdSBZdXL5n39JXlQc7QL3w",
         "x5u": "https://example.com/testing.crt",
-        "x5c": "---BEGIN CERTIFICATE---...",
+        "x5c": ["---BEGIN CERTIFICATE---..."],
         "x5t": "aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d",
         "x5t#S256": "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
     }"#;