diff --git a/libavcodec/hqxdsp.h b/libavcodec/hqxdsp.h
index a4755d156a..163c1f8ab2 100644
--- a/libavcodec/hqxdsp.h
+++ b/libavcodec/hqxdsp.h
@@ -26,6 +26,7 @@
 #ifndef AVCODEC_HQXDSP_H
 #define AVCODEC_HQXDSP_H
 
+#include <stddef.h>
 #include <stdint.h>
 
 typedef struct HQXDSPContext {