diff --git a/include/ghostty.h b/include/ghostty.h
index d81e3d19a..2feb35ad9 100644
--- a/include/ghostty.h
+++ b/include/ghostty.h
@@ -13,6 +13,7 @@ extern "C" {
 #endif
 
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
 //-------------------------------------------------------------------