2 files changed, 13 insertions, 4 deletions

diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py
index 8fe302ab49..8719f443c5 100644
--- a/scripts/lib/wic/filemap.py
+++ b/scripts/lib/wic/filemap.py
@@ -530,9 +530,18 @@ def filemap(image, log=None):
     except ErrorNotSupp:
         return FilemapSeek(image, log)
 
-def sparse_copy(src_fname, dst_fname, offset=0, skip=0,
+def sparse_copy(src_fname, dst_fname, skip=0, seek=0,
                 length=0, api=None):
-    """Efficiently copy sparse file to or into another file."""
+    """
+    Efficiently copy sparse file to or into another file.
+
+    src_fname: path to source file
+    dst_fname: path to destination file
+    skip: skip N bytes at thestart of src
+    seek: seek N bytes from the start of dst
+    length: read N bytes from src and write them to dst
+    api: FilemapFiemap or FilemapSeek object
+    """
     if not api:
         api = filemap
     fmap = api(src_fname)
@@ -554,7 +563,7 @@ def sparse_copy(src_fname, dst_fname, offset=0, skip=0,
             start = skip
 
         fmap._f_image.seek(start, os.SEEK_SET)
-        dst_file.seek(offset + start - skip, os.SEEK_SET)
+        dst_file.seek(seek + start - skip, os.SEEK_SET)
 
         chunk_size = 1024 * 1024
         to_read = end - start
diff --git a/scripts/lib/wic/plugins/imager/direct.py b/scripts/lib/wic/plugins/imager/direct.py
index f2e6127331..3cdedd1579 100644
--- a/scripts/lib/wic/plugins/imager/direct.py
+++ b/scripts/lib/wic/plugins/imager/direct.py
@@ -550,7 +550,7 @@ class PartitionedImage():
             source = part.source_file
             if source:
                 # install source_file contents into a partition
-                sparse_copy(source, self.path, part.start * self.sector_size)
+                sparse_copy(source, self.path, seek=part.start * self.sector_size)
 
                 logger.debug("Installed %s in partition %d, sectors %d-%d, "
                              "size %d sectors", source, part.num, part.start,