diff --git a/tools/libvchan/vchan-socket-proxy.c b/tools/libvchan/vchan-socket-proxy.c
index 29a12260ed..cd7629bc4e 100644
--- a/tools/libvchan/vchan-socket-proxy.c
+++ b/tools/libvchan/vchan-socket-proxy.c
@@ -326,7 +326,9 @@ int data_loop(struct vchan_proxy_state *state)
                 while (outsiz)
                     socket_wr(state->output_fd);
                 close(state->output_fd);
+                state->output_fd = -1;
                 close(state->input_fd);
+                state->input_fd = -1;
                 discard_buffers(state->ctrl);
                 break;
             }