diff --git a/src/mumble/AudioPreprocessor.h b/src/mumble/AudioPreprocessor.h
index 176ae24a10..8adefb2c54 100644
--- a/src/mumble/AudioPreprocessor.h
+++ b/src/mumble/AudioPreprocessor.h
@@ -6,6 +6,7 @@
 #ifndef MUMBLE_MUMBLE_AUDIOPREPROCESSOR_H_
 #define MUMBLE_MUMBLE_AUDIOPREPROCESSOR_H_
 
+#include <cstddef>
 #include <cstdint>
 #include <vector>