diff --git a/segpy/binary_reel_header_definition.py b/segpy/binary_reel_header_definition.py
index bb8b0c9..2979750 100644
--- a/segpy/binary_reel_header_definition.py
+++ b/segpy/binary_reel_header_definition.py
@@ -53,6 +53,7 @@ HEADER_DEF["DataSampleFormat"]["datatype"][SEGY_REVISION_1] = {
 HEADER_DEF["EnsembleFold"] = {"pos": 3226, "type": "int16", "def": 0}
 HEADER_DEF["TraceSorting"] = {"pos": 3228, "type": "int16", "def": 0}
 HEADER_DEF["VerticalSumCode"] = {"pos": 3230, "type": "int16", "def": 0}
+HEADER_DEF["SweepFrequencyStart"] = {"pos": 3232, "type": "int16", "def": 0}
 HEADER_DEF["SweepFrequencyEnd"] = {"pos": 3234, "type": "int16", "def": 0}
 HEADER_DEF["SweepLength"] = {"pos": 3236, "type": "int16", "def": 0}
 HEADER_DEF["SweepType"] = {"pos": 3238, "type": "int16", "def": 0}