diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 866738c2a7..1fc93cc255 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -23220,6 +23220,7 @@ static struct sip_peer *build_peer(const char *name, struct ast_variable *v, str
 	struct sip_peer tmp_peer;
 	const char *srvlookup = NULL;
 	static int deprecation_warning = 1;
+	int alt_fullcontact = alt ? 1 : 0;
 	struct ast_str *fullcontact = ast_str_alloca(512);
 
 	if (!realtime || ast_test_flag(&global_flags[1], SIP_PAGE2_RTCACHEFRIENDS)) {
@@ -23310,6 +23311,15 @@ static struct sip_peer *build_peer(const char *name, struct ast_variable *v, str
 		} else if (realtime && !strcasecmp(v->name, "name"))
 			ast_copy_string(peer->name, v->value, sizeof(peer->name));
 		else if (realtime && !strcasecmp(v->name, "fullcontact")) {
+			if (alt_fullcontact && !alt) {
+				/* Reset, because the alternate also has a fullcontact and we
+				 * do NOT want the field value to be doubled. It might be
+				 * tempting to skip this, but the first table might not have
+				 * fullcontact and since we're here, we know that the alternate
+				 * absolutely does. */
+				alt_fullcontact = 0;
+				ast_str_reset(fullcontact);
+			}
 			/* Reconstruct field, because realtime separates our value at the ';' */
 			if (fullcontact->used > 0) {
 				ast_str_append(&fullcontact, 0, ";%s", v->value);