diff --git a/tb/libtb.c b/tb/libtb.c
index c28b3142..ed534d87 100644
--- a/tb/libtb.c
+++ b/tb/libtb.c
@@ -1,3 +1,4 @@
+#include <stddef.h>
 // This is the TB unity build
 void* tb_jit_stack_create(size_t);