diff --git a/src/c/tcp.d b/src/c/tcp.d
index 109486b95..aff9d146f 100644
--- a/src/c/tcp.d
+++ b/src/c/tcp.d
@@ -277,7 +277,7 @@ si_open_client_stream(cl_object host, cl_object port)
 
   if (ecl_unlikely(!ECL_FIXNUMP(port) ||
                    ecl_fixnum_minusp(port) ||
-                   ecl_fixnum_greater(port,ecl_make_fixnum(65536)))) {
+                   ecl_fixnum_greater(port,ecl_make_fixnum(65535)))) {
     FEwrong_type_nth_arg(@[si::open-client-stream], 2, port,
                          ecl_read_from_cstring("(INTEGER 0 65535)"));
   }
@@ -311,7 +311,7 @@ si_open_server_stream(cl_object port)
 
   if (ecl_unlikely(!ECL_FIXNUMP(port) ||
                    ecl_fixnum_minusp(port) ||
-                   ecl_fixnum_greater(port,ecl_make_fixnum(65536)))) {
+                   ecl_fixnum_greater(port,ecl_make_fixnum(65535)))) {
     FEwrong_type_only_arg(@[si::open-client-stream], port,
                           ecl_read_from_cstring("(INTEGER 0 65535)"));
   }