diff --git a/src/os_unix.c b/src/os_unix.c
index 5efb5d1..2851459 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -4276,7 +4276,7 @@
 /*
  * Send SIGINT to a child process if "c" is an interrupt character.
  */
-    void
+    static void
 may_send_sigint(int c UNUSED, pid_t pid UNUSED, pid_t wpid UNUSED)
 {
 # ifdef SIGINT