diff --git a/sudio/rateshift/inc/rateshift.hpp b/sudio/rateshift/inc/rateshift.hpp
index c1d4ec6..e5e4be6 100644
--- a/sudio/rateshift/inc/rateshift.hpp
+++ b/sudio/rateshift/inc/rateshift.hpp
@@ -10,6 +10,7 @@
 #include <samplerate.h>
 #include <functional>
 #include <vector>
+#include <cstddef>
 
 namespace rateshift {
 
@@ -57,4 +58,4 @@ class CallbackResampler {
 
 std::vector<float> resample(const std::vector<float>& input, double sr_ratio, ConverterType converter_type, int channels);
 
-}
\ No newline at end of file
+}