diff --git a/src/sysdep.c b/src/sysdep.c
index 2cf7123018c..240b0f8a6b0 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -879,6 +879,7 @@ init_sigio (fd)
   interrupts_deferred = 0;
 }
 
+void
 reset_sigio ()
 {
   unrequest_sigio ();