diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 7a5f462..a8e4f41 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2743,7 +2743,7 @@
             return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_KEY_EXCHANGE );
         }
 
-        ssl->handshake->pmslen = ssl->handshake->dhm_ctx.len;
+        ssl->handshake->pmslen = POLARSSL_PREMASTER_SIZE;
 
         if( ( ret = dhm_calc_secret( &ssl->handshake->dhm_ctx,
                                       ssl->handshake->premaster,