diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 1d683d3..b09a7ab 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1269,7 +1269,7 @@
         return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
     }
 
-    if( ssl->in_hslen > 39 + n )
+    if( ssl->in_hslen > mbedtls_ssl_hs_hdr_len( ssl ) + 39 + n )
     {
         ext_len = ( ( buf[38 + n] <<  8 )
                   | ( buf[39 + n]       ) );
@@ -1281,7 +1281,7 @@
             return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
         }
     }
-    else if( ssl->in_hslen == 38 + n )
+    else if( ssl->in_hslen == mbedtls_ssl_hs_hdr_len( ssl ) + 38 + n )
     {
         ext_len = 0;
     }