diff --git a/src/sdp.c b/src/sdp.c
index 17eb577..9bb55d4 100644
--- a/src/sdp.c
+++ b/src/sdp.c
@@ -163,16 +163,35 @@ bool sdp_extract_sdp(struct sip_call_leg *leg, const sip_t *sip, bool any_codec)
 	return true;
 }
 
-char *sdp_create_file(struct sip_call_leg *leg, struct call_leg *other)
+char *sdp_create_file(struct sip_call_leg *leg, struct call_leg *other, sdp_mode_t mode)
 {
 	struct in_addr net = { .s_addr = htonl(other->ip) };
 	char *fmtp_str = NULL, *sdp;
+	char *mode_attribute;
 
 	leg->wanted_codec = app_media_name(other->payload_msg_type);
 
 	if (strcmp(leg->wanted_codec, "AMR") == 0)
 		fmtp_str = talloc_asprintf(leg, "a=fmtp:%d octet-align=1\r\n", other->payload_type);
 
+	switch (mode) {
+		case sdp_inactive:
+			mode_attribute = "a=inactive\r\n";
+			break;
+		case sdp_sendrecv:
+			mode_attribute = "a=sendrecv\r\n";
+			break;
+		case sdp_sendonly:
+			mode_attribute = "a=sendonly\r\n";
+			break;
+		case sdp_recvonly:
+			mode_attribute = "a=recvonly\r\n";
+			break;
+		default:
+			OSMO_ASSERT(false);
+			break;
+	}
+
 	sdp = talloc_asprintf(leg,
 				"v=0\r\n"
 				"o=Osmocom 0 0 IN IP4 %s\r\n"
@@ -181,12 +200,14 @@ char *sdp_create_file(struct sip_call_leg *leg, struct call_leg *other)
 				"t=0 0\r\n"
 				"m=audio %d RTP/AVP %d\r\n"
 				"%s"
-				"a=rtpmap:%d %s/8000\r\n",
+				"a=rtpmap:%d %s/8000\r\n"
+				"%s",
 				inet_ntoa(net), inet_ntoa(net), /* never use diff. addr! */
 				other->port, other->payload_type,
 				fmtp_str ? fmtp_str : "",
 				other->payload_type,
-				leg->wanted_codec);
+				leg->wanted_codec,
+				mode_attribute);
 	talloc_free(fmtp_str);
 	return sdp;
 }
diff --git a/src/sdp.h b/src/sdp.h
index d716644..72ff6b7 100644
--- a/src/sdp.h
+++ b/src/sdp.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <sofia-sip/sip.h>
+#include <sofia-sip/sdp.h>
 
 #include <stdbool.h>
 
@@ -10,4 +11,4 @@ struct call_leg;
 bool sdp_screen_sdp(const sip_t *sip);
 bool sdp_extract_sdp(struct sip_call_leg *leg, const sip_t *sip, bool any_codec);
 
-char *sdp_create_file(struct sip_call_leg *, struct call_leg *);
+char *sdp_create_file(struct sip_call_leg *, struct call_leg *, sdp_mode_t mode);
diff --git a/src/sip.c b/src/sip.c
index adf20d8..21401c6 100644
--- a/src/sip.c
+++ b/src/sip.c
@@ -28,6 +28,7 @@
 
 #include <sofia-sip/sip_status.h>
 #include <sofia-sip/su_log.h>
+#include <sofia-sip/sdp.h>
 
 #include <talloc.h>
 
@@ -385,7 +386,7 @@ static void sip_connect_call(struct call_leg *_leg)
 		return;
 	}
 
-	sdp = sdp_create_file(leg, other);
+	sdp = sdp_create_file(leg, other, sdp_sendrecv);
 
 	leg->state = SIP_CC_CONNECTED;
 	nua_respond(leg->nua_handle, SIP_200_OK,
@@ -425,7 +426,7 @@ static int send_invite(struct sip_agent *agent, struct sip_call_leg *leg,
 				called_num,
 				agent->app->sip.remote_addr,
 				agent->app->sip.remote_port);
-	char *sdp = sdp_create_file(leg, other);
+	char *sdp = sdp_create_file(leg, other, sdp_sendrecv);
 
 	leg->state = SIP_CC_INITIAL;
 	leg->dir = SIP_DIR_MT;