diff --git a/libs/acn/RDMPDU.cpp b/libs/acn/RDMPDU.cpp
index cab7d20a5..5c47cbb1e 100644
--- a/libs/acn/RDMPDU.cpp
+++ b/libs/acn/RDMPDU.cpp
@@ -47,7 +47,7 @@ void RDMPDU::PackData(ola::io::OutputStream *stream) const {
 void RDMPDU::PrependPDU(ola::io::IOStack *stack) {
   uint8_t vector = HostToNetwork(ola::rdm::START_CODE);
   stack->Write(reinterpret_cast<uint8_t*>(&vector), sizeof(vector));
-  PrependFlagsAndLength(stack);
+  PrependFlagsAndLength(stack, VFLAG_MASK | HFLAG_MASK | DFLAG_MASK, true);
 }
 }  // namespace acn
 }  // namespace ola
diff --git a/libs/acn/RDMPDUTest.cpp b/libs/acn/RDMPDUTest.cpp
index ff6489d0f..f11160f6b 100644
--- a/libs/acn/RDMPDUTest.cpp
+++ b/libs/acn/RDMPDUTest.cpp
@@ -161,7 +161,7 @@ void RDMPDUTest::testPrepend() {
   uint8_t *buffer = new uint8_t[length];
   OLA_ASSERT(stack.Read(buffer, length));
 
-  const uint8_t expected_data[] = {0x70, 3, TEST_VECTOR};
+  const uint8_t expected_data[] = {0xf0, 0, 4, TEST_VECTOR};
   OLA_ASSERT_DATA_EQUALS(expected_data, sizeof(expected_data), buffer, length);
   delete[] buffer;
 }