diff --git a/src/picopng/picopng.hpp b/src/picopng/picopng.hpp
index 76c280c..54cc727 100644
--- a/src/picopng/picopng.hpp
+++ b/src/picopng/picopng.hpp
@@ -1,4 +1,5 @@
 #pragma once
+#include <stddef.h>
 #include <vector>
 int decodePNG(unsigned char*& out_image, int& image_width, int& image_height,
     const unsigned char* in_png, size_t in_size,