diff --git a/include/nuttx/lib/stdatomic.h b/include/nuttx/lib/stdatomic.h
index 64a581860c2..07f14911fb9 100644
--- a/include/nuttx/lib/stdatomic.h
+++ b/include/nuttx/lib/stdatomic.h
@@ -29,6 +29,7 @@
 
 #include <stdint.h>
 #include <stdbool.h>
+#include <stddef.h>
 
 /****************************************************************************
  * Pre-processor Definitions