diff --git a/tests/libqtest.c b/tests/libqtest.c
index 512c150266..84ecbd2bd8 100644
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -446,6 +446,14 @@ void qmp_fd_sendv(int fd, const char *fmt, va_list ap)
     va_list ap_copy;
     QObject *qobj;
 
+    /* qobject_from_jsonv() silently eats leading 0xff as invalid
+     * JSON, but we want to test sending them over the wire to force
+     * resyncs */
+    if (*fmt == '\377') {
+        socket_send(fd, fmt, 1);
+        fmt++;
+    }
+
     /* Going through qobject ensures we escape strings properly.
      * This seemingly unnecessary copy is required in case va_list
      * is an array type.
diff --git a/tests/test-qga.c b/tests/test-qga.c
index c780f0079a..c77f241036 100644
--- a/tests/test-qga.c
+++ b/tests/test-qga.c
@@ -146,14 +146,30 @@ static void test_qga_sync_delimited(gconstpointer fix)
     QDict *ret;
     gchar *cmd;
 
-    cmd = g_strdup_printf("%c{'execute': 'guest-sync-delimited',"
-                          " 'arguments': {'id': %u } }", 0xff, r);
+    cmd = g_strdup_printf("\xff{'execute': 'guest-sync-delimited',"
+                          " 'arguments': {'id': %u } }", r);
     qmp_fd_send(fixture->fd, cmd);
     g_free(cmd);
 
-    v = read(fixture->fd, &c, 1);
-    g_assert_cmpint(v, ==, 1);
-    g_assert_cmpint(c, ==, 0xff);
+    /*
+     * Read and ignore garbage until resynchronized.
+     *
+     * Note that the full reset sequence would involve checking the
+     * response of guest-sync-delimited and repeating the loop if
+     * 'id' field of the response does not match the 'id' field of
+     * the request. Testing this fully would require inserting
+     * garbage in the response stream and is left as a future test
+     * to implement.
+     *
+     * TODO: The server shouldn't emit so much garbage (among other
+     * things, it loudly complains about the client's \xff being
+     * invalid JSON, even though it is a documented part of the
+     * handshake.
+     */
+    do {
+        v = read(fixture->fd, &c, 1);
+        g_assert_cmpint(v, ==, 1);
+    } while (c != 0xff);
 
     ret = qmp_fd_receive(fixture->fd);
     g_assert_nonnull(ret);
@@ -172,8 +188,19 @@ static void test_qga_sync(gconstpointer fix)
     QDict *ret;
     gchar *cmd;
 
-    cmd = g_strdup_printf("%c{'execute': 'guest-sync',"
-                          " 'arguments': {'id': %u } }", 0xff, r);
+    /*
+     * TODO guest-sync is inherently limited: we cannot distinguish
+     * failure caused by reacting to garbage on the wire prior to this
+     * command, from failure of this actual command. Clients are
+     * supposed to be able to send a raw '\xff' byte to at least
+     * re-synchronize the server's parser prior to this command, but
+     * we are not in a position to test that here because (at least
+     * for now) it causes the server to issue an error message about
+     * invalid JSON. Testing of '\xff' handling is done in
+     * guest-sync-delimited instead.
+     */
+    cmd = g_strdup_printf("{'execute': 'guest-sync',"
+                          " 'arguments': {'id': %u } }", r);
     ret = qmp_fd(fixture->fd, cmd);
     g_free(cmd);