diff --git a/SignalProcessing/FIRFilter.cpp b/SignalProcessing/FIRFilter.cpp
index cc85a7dfa..48bd3e5f1 100644
--- a/SignalProcessing/FIRFilter.cpp
+++ b/SignalProcessing/FIRFilter.cpp
@@ -9,7 +9,6 @@
 #include "FIRFilter.hpp"
 
 #include <cmath>
-#include <cstddef>
 
 #ifndef M_PI
 #define M_PI 3.1415926f
diff --git a/SignalProcessing/FIRFilter.hpp b/SignalProcessing/FIRFilter.hpp
index 5d473c070..d1899033a 100644
--- a/SignalProcessing/FIRFilter.hpp
+++ b/SignalProcessing/FIRFilter.hpp
@@ -17,6 +17,7 @@
 #define USE_ACCELERATE
 #endif
 
+#include <cstddef>
 #include <vector>
 
 namespace SignalProcessing {