diff --git a/libavcodec/cabac_functions.h b/libavcodec/cabac_functions.h
index bb2b4210b7..46af921822 100644
--- a/libavcodec/cabac_functions.h
+++ b/libavcodec/cabac_functions.h
@@ -27,6 +27,7 @@
 #ifndef AVCODEC_CABAC_FUNCTIONS_H
 #define AVCODEC_CABAC_FUNCTIONS_H
 
+#include <stddef.h>
 #include <stdint.h>
 
 #include "cabac.h"
diff --git a/libavcodec/x86/cabac.h b/libavcodec/x86/cabac.h
index cfd3b759c9..53d74c541e 100644
--- a/libavcodec/x86/cabac.h
+++ b/libavcodec/x86/cabac.h
@@ -21,6 +21,8 @@
 #ifndef AVCODEC_X86_CABAC_H
 #define AVCODEC_X86_CABAC_H
 
+#include <stddef.h>
+
 #include "libavcodec/cabac.h"
 #include "libavutil/attributes.h"
 #include "libavutil/macros.h"