diff --git a/webvttparser.cc b/webvttparser.cc
index 655252c..c79d642 100644
--- a/webvttparser.cc
+++ b/webvttparser.cc
@@ -6,8 +6,12 @@
 // in the file PATENTS.  All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 
-#include "./webvttparser.h"  // NOLINT
+#include "webvttparser.h"
+
+#include <ctype.h>
+
 #include <climits>
+#include <cstddef>
 
 namespace libwebvtt {