diff --git a/src/ethernetII.cpp b/src/ethernetII.cpp
index 99721ab..5f824f4 100644
--- a/src/ethernetII.cpp
+++ b/src/ethernetII.cpp
@@ -161,7 +161,9 @@ void EthernetII::write_serialization(uint8_t *buffer, uint32_t total_sz, const P
         Constants::Ethernet::e flag = Internals::pdu_flag_to_ether_type(
             inner_pdu()->pdu_type()
         );
-        payload_type(static_cast<uint16_t>(flag));
+        if (flag != Constants::Ethernet::UNKNOWN) {
+            payload_type(static_cast<uint16_t>(flag));
+        }
     }
     memcpy(buffer, &_eth, sizeof(ethhdr));
     uint32_t trailer = trailer_size();
diff --git a/tests/src/ethernetII.cpp b/tests/src/ethernetII.cpp
index c67d367..56bd3f8 100644
--- a/tests/src/ethernetII.cpp
+++ b/tests/src/ethernetII.cpp
@@ -158,3 +158,13 @@ TEST_F(EthernetIITest, EliminateEthernetPadding) {
     ASSERT_TRUE(eth.find_pdu<TCP>() != NULL);
     ASSERT_FALSE(eth.find_pdu<RawPDU>() != NULL);
 }
+
+TEST_F(EthernetIITest, SerializePreservesGivenPayloadType) {
+    EthernetII eth;
+    uint32_t payload_size = 100;
+    uint8_t payload[100] = {0};
+    eth /= RawPDU(payload, payload_size);
+    eth.payload_type(p_type);
+    eth.serialize();
+    EXPECT_EQ(p_type, eth.payload_type());
+}
\ No newline at end of file