diff --git a/library/x509parse.c b/library/x509parse.c
index 9e05f98..6239698 100644
--- a/library/x509parse.c
+++ b/library/x509parse.c
@@ -637,7 +637,9 @@
     switch( pk_alg )
     {
         case POLARSSL_PK_NONE:
-            ret = POLARSSL_ERR_X509_UNKNOWN_PK_ALG;
+        case POLARSSL_PK_ECDSA:
+            /* Should never happen */
+            ret = POLARSSL_ERR_X509_CERT_INVALID_ALG;
             break;
 
         case POLARSSL_PK_RSA: