diff --git a/prctl.c b/prctl.c
index 2dcda79..01c542f 100644
--- a/prctl.c
+++ b/prctl.c
@@ -27,3 +27,4 @@
 #include <pwd.h>
-#include <linux/prctl.h>
+#include <linux/prctl.h> /* prctl constants */
+#include <sys/prctl.h> /* prctl() proto */
 #include <string.h>
@@ -50,3 +51,3 @@ int verbose=0;
 
-print_version(char *progname)
+void print_version(char *progname)
 {
@@ -55,3 +56,3 @@ print_version(char *progname)
 
-usage(char *progname)
+void usage(char *progname)
 {