diff --git a/proxmox-acme/src/account.rs b/proxmox-acme/src/account.rs
index 0f023224..6993b2cf 100644
--- a/proxmox-acme/src/account.rs
+++ b/proxmox-acme/src/account.rs
@@ -323,7 +323,12 @@ impl AccountCreator {
 
     /// Set the EAB credentials for the account registration
     pub fn set_eab_credentials(mut self, kid: String, hmac_key: String) -> Result<Self, Error> {
-        let hmac_key = PKey::hmac(&base64::decode(hmac_key)?)?;
+        let hmac_key = if hmac_key.contains('+') || hmac_key.contains('/') {
+            base64::decode(hmac_key)?
+        } else {
+            b64u::decode(&hmac_key)?
+        };
+        let hmac_key = PKey::hmac(&hmac_key)?;
         self.eab_credentials = Some((kid, hmac_key));
         Ok(self)
     }
diff --git a/proxmox-acme/src/b64u.rs b/proxmox-acme/src/b64u.rs
index a4f8ce0a..9616fc1b 100644
--- a/proxmox-acme/src/b64u.rs
+++ b/proxmox-acme/src/b64u.rs
@@ -7,6 +7,11 @@ pub fn encode(data: &[u8]) -> String {
     base64::encode_config(data, config())
 }
 
+/// Decode a base64url encoded string.
+pub fn decode<T: AsRef<[u8]>>(data: &T) -> Result<Vec<u8>, crate::Error> {
+    Ok(base64::decode_config(data.as_ref(), config())?)
+}
+
 // curiously currently unused as we don't deserialize any of that
 // /// Decode bytes from a base64url string.
 // pub fn decode(data: &str) -> Result<Vec<u8>, base64::DecodeError> {