1 files changed, 1 insertions, 0 deletions
diff --git a/signal.c b/signal.c
index 96277e322c..31f0141267 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"
 #include "eval_intern.h"
 #include "internal.h"