diff --git a/src/MeshCore.h b/src/MeshCore.h
index 2db1d4c3e..2a786f222 100644
--- a/src/MeshCore.h
+++ b/src/MeshCore.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <stdint.h>
+#include <stddef.h>
 #include <math.h>
 
 #define MAX_HASH_SIZE        8