1 files changed, 1 insertions, 0 deletions

diff --git a/hex.c b/hex.c
index 58e2d70..357b996 100644
--- a/hex.c
+++ b/hex.c
@@ -7,6 +7,7 @@
  */
 
 #include <stdio.h>
+#include <stddef.h>
 #include <ctype.h>
 
 #include <X11/Xlib.h>