diff --git a/Parser/intrcheck.c b/Parser/intrcheck.c
index 5d02d17..5213573 100644
--- a/Parser/intrcheck.c
+++ b/Parser/intrcheck.c
@@ -125,6 +125,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 
 static int interrupted;