diff --git a/include/libbb.h b/include/libbb.h
index 0016d839f..91d458f50 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stddef.h>
 #include <string.h>
 #include <strings.h>
 #include <sys/ioctl.h>