diff --git a/glib/gspawn.c b/glib/gspawn.c
index 0ddd53249..d2ef460ab 100644
--- a/glib/gspawn.c
+++ b/glib/gspawn.c
@@ -1811,6 +1811,8 @@ do_posix_spawn (const gchar * const *argv,
     goto out_close_fds;
 
   duped_source_fds = g_new (gint, n_fds);
+  for (i = 0; i < n_fds; i++)
+    duped_source_fds[i] = -1;  /* initialise in case dupfd_cloexec() fails below */
   for (i = 0; i < n_fds; i++)
     {
       duped_source_fds[i] = dupfd_cloexec (source_fds[i], max_target_fd + 1);