diff --git a/lib/sp-capture-writer.c b/lib/sp-capture-writer.c
index 564437d9..15dcfbb0 100644
--- a/lib/sp-capture-writer.c
+++ b/lib/sp-capture-writer.c
@@ -375,6 +375,9 @@ sp_capture_writer_new_from_fd (int   fd,
   g_assert (fd != -1);
   g_assert (buffer_size % getpagesize() == 0);
 
+  if (ftruncate (fd, 0) != 0)
+    return NULL;
+
   self = g_new0 (SpCaptureWriter, 1);
   self->ref_count = 1;
   self->fd = fd;