--- hackbench.c
+++ hackbench.c
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#include <unistd.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
@@ -145,7 +146,7 @@
 
 int main(int argc, char *argv[])
 {
-        unsigned int i, num_groups, total_children;
+        unsigned int i, num_groups = 0, total_children;
         struct timeval start, stop, diff;
         unsigned int num_fds = 20;
         int readyfds[2], wakefds[2];