diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 5f01a01bc..f6d014bc5 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2888,7 +2888,8 @@ static int ssl_parse_encrypted_pms( ssl_context *ssl,
     unsigned char *pms = ssl->handshake->premaster + pms_offset;
     unsigned char fake_pms[48], peer_pms[48];
     unsigned char mask;
-    size_t i, diff, peer_pmslen;
+    size_t i, peer_pmslen;
+    unsigned int diff;
 
     if( ! pk_can_do( ssl_own_key( ssl ), POLARSSL_PK_RSA ) )
     {
@@ -2934,7 +2935,7 @@ static int ssl_parse_encrypted_pms( ssl_context *ssl,
                       sizeof( peer_pms ),
                       ssl->f_rng, ssl->p_rng );
 
-    diff  = (size_t) ret;
+    diff  = (unsigned int) ret;
     diff |= peer_pmslen ^ 48;
     diff |= peer_pms[0] ^ ssl->handshake->max_major_ver;
     diff |= peer_pms[1] ^ ssl->handshake->max_minor_ver;
@@ -2952,8 +2953,8 @@ static int ssl_parse_encrypted_pms( ssl_context *ssl,
     }
     ssl->handshake->pmslen = 48;
 
-    mask = ( diff | - diff ) >> ( sizeof( size_t ) * 8 - 1 );
-    mask = (unsigned char)( - ( ret != 0 ) ); /* mask = diff ? 0xff : 0x00 */
+    /* mask = diff ? 0xff : 0x00 */
+    mask = - ( diff | - diff ) >> ( sizeof( unsigned int ) * 8 - 1 );
     for( i = 0; i < ssl->handshake->pmslen; i++ )
         pms[i] = ( mask & fake_pms[i] ) | ( (~mask) & peer_pms[i] );