diff --git a/hw/xquartz/pbproxy/main.m b/hw/xquartz/pbproxy/main.m
index 560cf0182..bb0646502 100644
--- a/hw/xquartz/pbproxy/main.m
+++ b/hw/xquartz/pbproxy/main.m
@@ -75,6 +75,8 @@ static int x_io_error_handler (Display *dpy) {
         exit(EXIT_FAILURE);
 #endif
 
+    /* Prevent _XIOError from calling exit() */
+    pthread_exit(NULL);
     return 0;
 }