diff --git a/io/channel-buffer.c b/io/channel-buffer.c
index 3e5117bf28..43d795976d 100644
--- a/io/channel-buffer.c
+++ b/io/channel-buffer.c
@@ -140,6 +140,7 @@ static int qio_channel_buffer_close(QIOChannel *ioc,
     QIOChannelBuffer *bioc = QIO_CHANNEL_BUFFER(ioc);
 
     g_free(bioc->data);
+    bioc->data = NULL;
     bioc->capacity = bioc->usage = bioc->offset = 0;
 
     return 0;