diff --git a/rubberband/RubberBandStretcher.h b/rubberband/RubberBandStretcher.h
index bee3717..1b99c00 100644
--- a/rubberband/RubberBandStretcher.h
+++ b/rubberband/RubberBandStretcher.h
@@ -21,6 +21,7 @@
 
 #include <vector>
 #include <map>
+#include <cstddef>
 
 /**
  * @mainpage RubberBand