diff --git a/src/server.cpp b/src/server.cpp
index af6fed3a0f..68b27513de 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -3750,7 +3750,11 @@ bool Server::dynamicAddMedia(const DynamicMediaArgs &a)
 	// Push file to existing clients
 	if (m_env) {
 		NetworkPacket pkt(TOCLIENT_MEDIA_PUSH, 0);
-		pkt << raw_hash << filename << static_cast<bool>(a.ephemeral);
+		pkt << raw_hash << filename;
+		// NOTE: the meaning of a.ephemeral was accidentally inverted between proto 39 and 40,
+		// when dynamic_add_media v2 was added. As of 5.12.0 the server sends it correctly again.
+		// Compatibility code on the client-side was not added.
+		pkt << static_cast<bool>(!a.ephemeral);
 
 		NetworkPacket legacy_pkt = pkt;