diff --git a/include/uk/mimalloc.h b/include/uk/mimalloc.h
index eadeae1..b2aa506 100644
--- a/include/uk/mimalloc.h
+++ b/include/uk/mimalloc.h
@@ -35,6 +35,7 @@
 #define __LIBMIMALLOC_H__
 
 #include <uk/alloc.h>
+#include <stddef.h>
 
 #ifdef __cplusplus
 extern "C" {