diff --git a/src/dec/webpi.h b/src/dec/webpi.h
index 7dba85f9..9ebafb15 100644
--- a/src/dec/webpi.h
+++ b/src/dec/webpi.h
@@ -16,8 +16,6 @@
 extern "C" {
 #endif
 
-#include <stddef.h>   // for size_t
-
 #include "../webp/decode_vp8.h"
 #include "../utils/rescaler.h"
 
diff --git a/src/dsp/cpu.c b/src/dsp/cpu.c
index 05bd6424..36a029a2 100644
--- a/src/dsp/cpu.c
+++ b/src/dsp/cpu.c
@@ -9,8 +9,6 @@
 //
 // Author: Christian Duvivier (cduvivier@google.com)
 
-#include <stddef.h>  // for NULL
-
 #include "./dsp.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/dsp/enc.c b/src/dsp/enc.c
index f07aa691..02234564 100644
--- a/src/dsp/enc.c
+++ b/src/dsp/enc.c
@@ -9,6 +9,7 @@
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
+#include <stdlib.h>  // for abs()
 #include "./dsp.h"
 #include "../enc/vp8enci.h"
 
diff --git a/src/utils/bit_reader.h b/src/utils/bit_reader.h
index 03b12371..05d2c274 100644
--- a/src/utils/bit_reader.h
+++ b/src/utils/bit_reader.h
@@ -14,7 +14,6 @@
 #define WEBP_UTILS_BIT_READER_H_
 
 #include <assert.h>
-#include <stddef.h>  // For size_t
 #ifdef _MSC_VER
 #include <stdlib.h>  // _byteswap_ulong
 #endif
diff --git a/src/utils/filters.c b/src/utils/filters.c
index 4844cc7a..08f52a3d 100644
--- a/src/utils/filters.c
+++ b/src/utils/filters.c
@@ -11,7 +11,6 @@
 
 #include "./filters.h"
 #include <assert.h>
-#include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/src/utils/huffman.h b/src/utils/huffman.h
index b7de7330..f9668ca2 100644
--- a/src/utils/huffman.h
+++ b/src/utils/huffman.h
@@ -13,7 +13,6 @@
 #define WEBP_UTILS_HUFFMAN_H_
 
 #include <assert.h>
-#include <stddef.h>
 #include "../webp/types.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/webp/decode_vp8.h b/src/webp/decode_vp8.h
index 6d391edc..dde7fc94 100644
--- a/src/webp/decode_vp8.h
+++ b/src/webp/decode_vp8.h
@@ -12,8 +12,6 @@
 #ifndef WEBP_WEBP_DECODE_VP8_H_
 #define WEBP_WEBP_DECODE_VP8_H_
 
-#include <stddef.h>  // for size_t
-
 #include "./decode.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/webp/encode.h b/src/webp/encode.h
index 772ac252..cabc9823 100644
--- a/src/webp/encode.h
+++ b/src/webp/encode.h
@@ -12,8 +12,6 @@
 #ifndef WEBP_WEBP_ENCODE_H_
 #define WEBP_WEBP_ENCODE_H_
 
-#include <stdlib.h>
-
 #include "./types.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/webp/types.h b/src/webp/types.h
index 5b80eac8..25c0e708 100644
--- a/src/webp/types.h
+++ b/src/webp/types.h
@@ -12,6 +12,8 @@
 #ifndef WEBP_WEBP_TYPES_H_
 #define WEBP_WEBP_TYPES_H_
 
+#include <stddef.h>  // for size_t
+
 #ifndef _MSC_VER
 #include <inttypes.h>
 #ifdef __STRICT_ANSI__