diff --git a/src/mod/applications/mod_spandsp/mod_spandsp_fax.c b/src/mod/applications/mod_spandsp/mod_spandsp_fax.c
index 2ea3eb00a3..9b8b051f50 100644
--- a/src/mod/applications/mod_spandsp/mod_spandsp_fax.c
+++ b/src/mod/applications/mod_spandsp/mod_spandsp_fax.c
@@ -789,9 +789,9 @@ static t38_mode_t negotiate_t38(pvt_t *pvt)
         t38_options->T38FaxRateManagement = "transferredTCF";
         t38_options->T38FaxMaxBuffer = 2000;
         t38_options->T38FaxMaxDatagram = LOCAL_FAX_MAX_DATAGRAM;
-        if (strcasecmp(t38_options->T38FaxUdpEC, "t38UDPRedundancy") == 0
-            ||
-            strcasecmp(t38_options->T38FaxUdpEC, "t38UDPFEC") == 0) {
+        if (!zstr(t38_options->T38FaxUdpEC) &&
+            (strcasecmp(t38_options->T38FaxUdpEC, "t38UDPRedundancy") == 0 ||
+             strcasecmp(t38_options->T38FaxUdpEC, "t38UDPFEC") == 0)) {
             t38_options->T38FaxUdpEC = "t38UDPRedundancy";
         } else {
             t38_options->T38FaxUdpEC = NULL;