diff --git a/tests/simulator-ng.pl b/tests/simulator-ng.pl
index 1885ddddd..32a4a38c9 100755
--- a/tests/simulator-ng.pl
+++ b/tests/simulator-ng.pl
@@ -275,9 +275,10 @@ sub rtcp_savpf {
 
 sub rtp {
 	my ($ctx) = @_;
+	my $ssrc = $$ctx{ssrc} // ($$ctx{ssrc} = rand(2**32));
 	my $seq = $$ctx{rtp_seqnum};
 	defined($seq) or $seq = int(rand(0xfffe)) + 1;
-	my $hdr = pack("CCnNN", 0x80, 0x00, $seq, rand(2**32), rand(2**32));
+	my $hdr = pack("CCnNN", 0x80, 0x00, $seq, rand(2**32), $ssrc);
 	my $pack = $hdr . rand_str($PAYLOAD);
 	$$ctx{rtp_seqnum} = (++$seq & 0xffff);
 	return $pack;