1 files changed, 1 insertions, 0 deletions
diff --git a/signal.c b/signal.c
index d4954fb21b..2e920f9f76 100644
--- a/signal.c
+++ b/signal.c
@@ -16,6 +16,7 @@
 #include <signal.h>
 #include <stdio.h>
 #include <errno.h>
+#include <unistd.h>
 #include "ruby_atomic.h"
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>