diff --git a/dix/rpcbuf.c b/dix/rpcbuf.c
index 6c275f0c70..91b706eb3d 100644
--- a/dix/rpcbuf.c
+++ b/dix/rpcbuf.c
@@ -99,6 +99,7 @@ Bool x_rpcbuf_write_string_pad(x_rpcbuf_t *rpcbuf, const char *str)
     return __x_rpcbuf_write_bin_pad(rpcbuf, str, strlen(str));
 }
 
+_X_EXPORT /* only for GLX, not part of public ABI */
 Bool x_rpcbuf_write_string_0t_pad(x_rpcbuf_t *rpcbuf, const char *str)
 {
     if (!str)