Does not compile on debian jessie

[Ophir LOJKINE]

While compiling in debian, I get this error:

driver.c: In function ‘process_options’:
driver.c:892:35: error: ‘pid_t’ undeclared (first use in this function)
   pids = malloc(children * sizeof(pid_t));
                                   ^

[luw2007]

diff --git a/driver.c b/driver.c
index 4f4c903..c5b50de 100644
--- a/driver.c
+++ b/driver.c
@@ -11,6 +11,7 @@
#ifndef DOS
#include <unistd.h>
#include <sys/wait.h>
+#include <sys/types.h>
#endif

#endif /* WIN32 */