diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 30be2922b6..3b2cbd0393 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -9652,7 +9652,7 @@ static enum sip_result add_sdp(struct sip_request *resp, struct sip_pvt *p, int
 
 		ast_str_append(&m_modem, 0, "m=image %d udptl t38", ntohs(udptldest.sin_port));
 
-		ast_str_append(&a_modem, 0, "a=T38Faxversion:%d\r\n", p->t38.our_parms.version);
+		ast_str_append(&a_modem, 0, "a=T38FaxVersion:%d\r\n", p->t38.our_parms.version);
 		ast_str_append(&a_modem, 0, "a=T38MaxBitRate:%d\r\n", t38_get_rate(p->t38.our_parms.rate));
 		if (p->t38.our_parms.fill_bit_removal) {
 			ast_str_append(&a_modem, 0, "a=T38FaxFillBitRemoval\r\n");