diff --git a/can/io/blf.py b/can/io/blf.py
index 77bd02fae..26cae7de5 100644
--- a/can/io/blf.py
+++ b/can/io/blf.py
@@ -49,10 +49,10 @@ class BLFParseError(Exception):
 OBJ_HEADER_BASE_STRUCT = struct.Struct("<4sHHLL")
 
 # flags, client index, object version, timestamp
-OBJ_HEADER_V1_STRUCT = struct.Struct("<LHHQ")
+OBJ_HEADER_V1_STRUCT = struct.Struct("<LHHq")
 
 # flags, timestamp status, object version, timestamp, (original timestamp)
-OBJ_HEADER_V2_STRUCT = struct.Struct("<LBxHQ8x")
+OBJ_HEADER_V2_STRUCT = struct.Struct("<LBxHq8x")
 
 # compression method, size uncompressed
 LOG_CONTAINER_STRUCT = struct.Struct("<H6xL4x")
diff --git a/doc/changelog.d/+blf_prerecording_timestamps.fixed.rst b/doc/changelog.d/+blf_prerecording_timestamps.fixed.rst
new file mode 100644
index 000000000..4a5a50703
--- /dev/null
+++ b/doc/changelog.d/+blf_prerecording_timestamps.fixed.rst
@@ -0,0 +1 @@
+changed interpretion of blf recording relative timestamps from unsigned to signed int64