diff --git a/src/include/netif/ppp/ppp.h b/src/include/netif/ppp/ppp.h
index eeb38201..a80dbb95 100644
--- a/src/include/netif/ppp/ppp.h
+++ b/src/include/netif/ppp/ppp.h
@@ -460,6 +460,9 @@ void ppp_set_notify_phase_callback(ppp_pcb *pcb, ppp_notify_phase_cb_fn notify_p
  *
  * Holdoff is the time to wait (in seconds) before initiating
  * the connection.
+ *
+ * If this port connects to a modem, the modem connection must be
+ * established before calling this.
  */
 err_t ppp_open(ppp_pcb *pcb, u16_t holdoff);
 
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index a96fc7d1..0834f84d 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -255,6 +255,9 @@ void ppp_set_notify_phase_callback(ppp_pcb *pcb, ppp_notify_phase_cb_fn notify_p
  *
  * Holdoff is the time to wait (in seconds) before initiating
  * the connection.
+ *
+ * If this port connects to a modem, the modem connection must be
+ * established before calling this.
  */
 err_t ppp_open(ppp_pcb *pcb, u16_t holdoff) {
   if (pcb->phase != PPP_PHASE_DEAD) {
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index 6221aa0a..b51c4a2f 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -167,9 +167,6 @@ ppp_get_fcs(u8_t byte)
 /*
  * Create a new PPP connection using the given serial I/O device.
  *
- * If this port connects to a modem, the modem connection must be
- * established before calling this.
- *
  * Return 0 on success, an error code on failure.
  */
 ppp_pcb *pppos_create(struct netif *pppif, sio_fd_t fd,