diff --git a/can/interfaces/socketcan/socketcan.py b/can/interfaces/socketcan/socketcan.py
index b9f58f089..51063c6a2 100644
--- a/can/interfaces/socketcan/socketcan.py
+++ b/can/interfaces/socketcan/socketcan.py
@@ -242,6 +242,8 @@ def build_can_frame(msg: Message) -> bytes:
         data_len = msg.dlc
     else:
         data_len = min(i for i in can.util.CAN_FD_DLC if i >= len(msg.data))
+    header = CAN_FRAME_HEADER_STRUCT.pack(can_id, data_len, flags, msg.dlc)
+    return header + data
 
 
 def build_bcm_header(
@@ -330,8 +332,7 @@ def dissect_can_frame(frame: bytes) -> Tuple[int, int, int, bytes]:
     # Allow deprecated can frames with old struct
     if (
         data_len == constants.CAN_MAX_DLEN
-        and len8_dlc > constants.CAN_MAX_DLEN
-        and len8_dlc <= constants.CAN_MAX_RAW_DLC
+        and constants.CAN_MAX_DLEN < len8_dlc <= constants.CAN_MAX_RAW_DLC
     ):
         can_dlc = len8_dlc
     else: