diff --git a/nagiostats.c b/nagiostats.c
index d80bf24..25c7f2d 100644
--- a/nagiostats.c
+++ b/nagiostats.c
@@ -4,6 +4,7 @@
  */
 
 #include <stdio.h>
+#include <stdbool.h>
 
 #if ! HAVE_CONFIG_H