diff --git a/src/add-ons/kernel/network/protocols/unix/UnixDatagramEndpoint.cpp b/src/add-ons/kernel/network/protocols/unix/UnixDatagramEndpoint.cpp
index c497705a72..1e0be05e18 100644
--- a/src/add-ons/kernel/network/protocols/unix/UnixDatagramEndpoint.cpp
+++ b/src/add-ons/kernel/network/protocols/unix/UnixDatagramEndpoint.cpp
@@ -215,6 +215,9 @@ UnixDatagramEndpoint::Send(const iovec* vecs, size_t vecCount,
 	TRACE("[%" B_PRId32 "] %p->UnixDatagramEndpoint::Send()\n",
 		find_thread(NULL), this);
 
+	if ((flags & ~(MSG_DONTWAIT)) != 0)
+		return EOPNOTSUPP;
+
 	bigtime_t timeout = 0;
 	if ((flags & MSG_DONTWAIT) == 0) {
 		timeout = absolute_timeout(socket->send.timeout);
@@ -325,6 +328,9 @@ UnixDatagramEndpoint::Receive(const iovec* vecs, size_t vecCount,
 	TRACE("[%" B_PRId32 "] %p->UnixDatagramEndpoint::Receive()\n",
 		find_thread(NULL), this);
 
+	if ((flags & ~(MSG_DONTWAIT)) != 0)
+		return EOPNOTSUPP;
+
 	bigtime_t timeout = 0;
 	if ((flags & MSG_DONTWAIT) == 0) {
 		timeout = absolute_timeout(socket->receive.timeout);
diff --git a/src/add-ons/kernel/network/protocols/unix/UnixStreamEndpoint.cpp b/src/add-ons/kernel/network/protocols/unix/UnixStreamEndpoint.cpp
index fc6e1a5e6b..698777bf80 100644
--- a/src/add-ons/kernel/network/protocols/unix/UnixStreamEndpoint.cpp
+++ b/src/add-ons/kernel/network/protocols/unix/UnixStreamEndpoint.cpp
@@ -379,6 +379,9 @@ UnixStreamEndpoint::Send(const iovec* vecs, size_t vecCount,
 	TRACE("[%" B_PRId32 "] %p->UnixStreamEndpoint::Send(%p, %ld, %p)\n",
 		find_thread(NULL), this, vecs, vecCount, ancillaryData);
 
+	if ((flags & ~(MSG_DONTWAIT)) != 0)
+		return EOPNOTSUPP;
+
 	bigtime_t timeout = 0;
 	if ((flags & MSG_DONTWAIT) == 0) {
 		timeout = absolute_timeout(socket->send.timeout);
@@ -473,6 +476,9 @@ UnixStreamEndpoint::Receive(const iovec* vecs, size_t vecCount,
 	TRACE("[%" B_PRId32 "] %p->UnixStreamEndpoint::Receive(%p, %ld)\n",
 		find_thread(NULL), this, vecs, vecCount);
 
+	if ((flags & ~(MSG_DONTWAIT)) != 0)
+		return EOPNOTSUPP;
+
 	bigtime_t timeout = 0;
 	if ((flags & MSG_DONTWAIT) == 0) {
 		timeout = absolute_timeout(socket->receive.timeout);