diff --git a/library/ecjpake.c b/library/ecjpake.c
index 8a8f0e2..4ffeaa3 100644
--- a/library/ecjpake.c
+++ b/library/ecjpake.c
@@ -355,6 +355,12 @@
      * } ECJPAKEKeyKP;
      */
     MBEDTLS_MPI_CHK( mbedtls_ecp_tls_read_point( grp, X, p, end - *p ) );
+    if( mbedtls_ecp_is_zero( X ) )
+    {
+        ret = MBEDTLS_ERR_ECP_INVALID_KEY;
+        goto cleanup;
+    }
+
     MBEDTLS_MPI_CHK( ecjpake_zkp_read( md_info, grp, G, X, id, p, end ) );
 
 cleanup: