diff --git a/os/dev/slip.c b/os/dev/slip.c
index 076685d58..db2e26ee4 100644
--- a/os/dev/slip.c
+++ b/os/dev/slip.c
@@ -84,7 +84,7 @@ slip_set_input_callback(void (*c)(void))
   input_callback = c;
 }
 /*---------------------------------------------------------------------------*/
-uint8_t
+void
 slip_send(void)
 {
   uint16_t i;
diff --git a/os/dev/slip.h b/os/dev/slip.h
index 1a9fb68ce..d4450d533 100644
--- a/os/dev/slip.h
+++ b/os/dev/slip.h
@@ -41,7 +41,7 @@ PROCESS_NAME(slip_process);
 /**
  * Send an IP packet from the uIP buffer with SLIP.
  */
-uint8_t slip_send(void);
+void slip_send(void);
 
 /**
  * Input a SLIP byte.