diff --git a/talk/base/scoped_ref_ptr.h b/talk/base/scoped_ref_ptr.h
index 3ce72cbce6..ae1ab0f230 100644
--- a/talk/base/scoped_ref_ptr.h
+++ b/talk/base/scoped_ref_ptr.h
@@ -80,6 +80,8 @@
 #ifndef TALK_BASE_SCOPED_REF_PTR_H_
 #define TALK_BASE_SCOPED_REF_PTR_H_
 
+#include <stddef.h>
+
 namespace talk_base {
 
 template <class T>