diff --git a/src/tja2fumen/parsers.py b/src/tja2fumen/parsers.py
index 37c73dd..a3c0d18 100644
--- a/src/tja2fumen/parsers.py
+++ b/src/tja2fumen/parsers.py
@@ -480,8 +480,7 @@ def parse_fumen(fumen_file: str,
 
 def read_struct(file: BinaryIO,
                 order: str,
-                format_string: str,
-                seek: int = 0) -> tuple[Any, ...]:
+                format_string: str) -> tuple[Any, ...]:
     """
     Interpret bytes as packed binary data.
 
@@ -497,8 +496,6 @@ def read_struct(file: BinaryIO,
         - interpreted_string: A string containing interpreted byte values,
                               based on the specified 'fmt' format characters.
     """
-    if seek:
-        file.seek(seek)
     expected_size = struct.calcsize(order + format_string)
     byte_string = file.read(expected_size)
     # One "official" fumen (AC11\deo\deo_n.bin) runs out of data early
diff --git a/src/tja2fumen/writers.py b/src/tja2fumen/writers.py
index 4bc4417..494e2bd 100644
--- a/src/tja2fumen/writers.py
+++ b/src/tja2fumen/writers.py
@@ -55,10 +55,7 @@ def write_fumen(path_out: str, song: FumenCourse) -> None:
 def write_struct(file: BinaryIO,
                  order: str,
                  format_string: str,
-                 value_list: list[Any],
-                 seek: int = 0) -> None:
+                 value_list: list[Any]) -> None:
     """Pack (int, float, etc.) values into a string of bytes, then write."""
-    if seek:
-        file.seek(seek)
     packed_bytes = struct.pack(order + format_string, *value_list)
     file.write(packed_bytes)