diff --git a/test/support/test_iterators.h b/test/support/test_iterators.h
index c6394434b..d8790fecb 100644
--- a/test/support/test_iterators.h
+++ b/test/support/test_iterators.h
@@ -12,6 +12,7 @@
 
 #include <iterator>
 #include <stdexcept>
+#include <cstddef>
 #include <cassert>
 
 #include "test_macros.h"