Keep gcc -Wall happy.
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 8219f75..7cdcf46 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -47,6 +47,10 @@
 #include "import.h"
 #include "marshal.h"
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 #ifdef HAVE_SIGNAL_H
 #include <signal.h>
 #endif