diff --git a/src/dec/webp.c b/src/dec/webp.c
index 34480474..ec05ff2f 100644
--- a/src/dec/webp.c
+++ b/src/dec/webp.c
@@ -14,7 +14,7 @@
 #include "./vp8i.h"
 #include "./vp8li.h"
 #include "./webpi.h"
-#include "../webp/format_constants.h"
+#include "../webp/mux_types.h"  // ALPHA_FLAG
 
 #if defined(__cplusplus) || defined(c_plusplus)
 extern "C" {
diff --git a/src/enc/syntax.c b/src/enc/syntax.c
index c157cafd..24e008c3 100644
--- a/src/enc/syntax.c
+++ b/src/enc/syntax.c
@@ -12,7 +12,8 @@
 #include <assert.h>
 
 #include "../utils/utils.h"
-#include "../webp/format_constants.h"
+#include "../webp/format_constants.h"  // RIFF constants
+#include "../webp/mux_types.h"         // ALPHA_FLAG
 #include "./vp8enci.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/webp/demux.h b/src/webp/demux.h
index 2a999cd0..cfb4fdfe 100644
--- a/src/webp/demux.h
+++ b/src/webp/demux.h
@@ -45,7 +45,6 @@
 #ifndef WEBP_WEBP_DEMUX_H_
 #define WEBP_WEBP_DEMUX_H_
 
-#include "./format_constants.h"
 #include "./mux_types.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/webp/format_constants.h b/src/webp/format_constants.h
index 2ac8fe67..8b3d6778 100644
--- a/src/webp/format_constants.h
+++ b/src/webp/format_constants.h
@@ -12,6 +12,9 @@
 #ifndef WEBP_WEBP_FORMAT_CONSTANTS_H_
 #define WEBP_WEBP_FORMAT_CONSTANTS_H_
 
+// Create fourcc of the chunk from the chunk tag characters.
+#define MKFOURCC(a, b, c, d) ((uint32_t)(a) | (b) << 8 | (c) << 16 | (d) << 24)
+
 // VP8 related constants.
 #define VP8_SIGNATURE 0x9d012a              // Signature in VP8 data.
 #define VP8_MAX_PARTITION0_SIZE (1 << 19)   // max size of mode partition
@@ -70,19 +73,6 @@ typedef enum {
 #define FRGM_CHUNK_SIZE    6     // Size of a FRGM chunk.
 #define VP8X_CHUNK_SIZE    10    // Size of a VP8X chunk.
 
-// VP8X Feature Flags.
-#if !(defined(__cplusplus) || defined(c_plusplus))
-typedef enum WebPFeatureFlags WebPFeatureFlags;
-#endif
-enum WebPFeatureFlags {
-  FRAGMENTS_FLAG  = 0x00000001,
-  ANIMATION_FLAG  = 0x00000002,
-  XMP_FLAG        = 0x00000004,
-  EXIF_FLAG       = 0x00000008,
-  ALPHA_FLAG      = 0x00000010,
-  ICCP_FLAG       = 0x00000020
-};
-
 #define MAX_CANVAS_SIZE     (1 << 24)    // 24-bit max for VP8X width/height.
 #define MAX_IMAGE_AREA      (1ULL << 32) // 32-bit max for width x height.
 #define MAX_LOOP_COUNT      (1 << 16)    // maximum value for loop-count
diff --git a/src/webp/mux.h b/src/webp/mux.h
index 713d738c..85a89227 100644
--- a/src/webp/mux.h
+++ b/src/webp/mux.h
@@ -45,7 +45,6 @@
 #ifndef WEBP_WEBP_MUX_H_
 #define WEBP_WEBP_MUX_H_
 
-#include "./format_constants.h"
 #include "./mux_types.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
diff --git a/src/webp/mux_types.h b/src/webp/mux_types.h
index 84d94472..4006a540 100644
--- a/src/webp/mux_types.h
+++ b/src/webp/mux_types.h
@@ -5,7 +5,7 @@
 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
 // -----------------------------------------------------------------------------
 //
-// Internal header for some common data-types used by mux and demux libraries.
+// Data-types common to the mux and demux libraries.
 //
 // Author: Urvang (urvang@google.com)
 
@@ -20,14 +20,23 @@
 extern "C" {
 #endif
 
-// Create fourcc of the chunk from the chunk tag characters.
-#define MKFOURCC(a, b, c, d) ((uint32_t)(a) | (b) << 8 | (c) << 16 | (d) << 24)
+#if !(defined(__cplusplus) || defined(c_plusplus))
+typedef enum WebPFeatureFlags WebPFeatureFlags;
+typedef enum WebPMuxAnimDispose WebPMuxAnimDispose;
+#endif
+
+// VP8X Feature Flags.
+enum WebPFeatureFlags {
+  FRAGMENTS_FLAG  = 0x00000001,
+  ANIMATION_FLAG  = 0x00000002,
+  XMP_FLAG        = 0x00000004,
+  EXIF_FLAG       = 0x00000008,
+  ALPHA_FLAG      = 0x00000010,
+  ICCP_FLAG       = 0x00000020
+};
 
 // Dispose method (animation only). Indicates how the area used by the current
 // frame is to be treated before rendering the next frame on the canvas.
-#if !(defined(__cplusplus) || defined(c_plusplus))
-typedef enum WebPMuxAnimDispose WebPMuxAnimDispose;
-#endif
 enum WebPMuxAnimDispose {
   WEBP_MUX_DISPOSE_NONE,       // Do not dispose.
   WEBP_MUX_DISPOSE_BACKGROUND  // Dispose to background color.