diff --git a/HydrantCAProxy/HydrantIdCAPlugin.cs b/HydrantCAProxy/HydrantIdCAPlugin.cs
index 6c7f86e..b1cb9fb 100644
--- a/HydrantCAProxy/HydrantIdCAPlugin.cs
+++ b/HydrantCAProxy/HydrantIdCAPlugin.cs
@@ -586,7 +586,7 @@ await flow.StepAsync("SubmitEnrollment", async () =>
                         };
                     }
 
-                    var previousX509 = new X509Certificate2(Encoding.ASCII.GetBytes(previousCert.Certificate));
+                    var previousX509 = new X509Certificate2(Convert.FromBase64String(previousCert.Certificate));
                     var expiration = previousX509.NotAfter;
                     var now = DateTime.UtcNow;