diff --git a/src/libsysprof-profile/sysprof-recording.c b/src/libsysprof-profile/sysprof-recording.c
index 53a245e3..d455fc34 100644
--- a/src/libsysprof-profile/sysprof-recording.c
+++ b/src/libsysprof-profile/sysprof-recording.c
@@ -414,7 +414,7 @@ sysprof_recording_add_file_fiber (gpointer user_data)
 
   while (len > 0)
     {
-      gsize to_write = MIN (len, 4096*8);
+      gsize to_write = MIN (len, ((4096*8)-sizeof (SysprofCaptureFileChunk)));
 
       if (!sysprof_capture_writer_add_file (add_file->writer,
                                             SYSPROF_CAPTURE_CURRENT_TIME,