diff --git a/src/mux/muxedit.c b/src/mux/muxedit.c
index cf3df63a..fdf46d14 100644
--- a/src/mux/muxedit.c
+++ b/src/mux/muxedit.c
@@ -643,9 +643,9 @@ WebPMuxError WebPMuxAssemble(WebPMux* const mux,
 
   // Main RIFF header.
   PutLE32(data + 0, mktag('R', 'I', 'F', 'F'));
-  PutLE32(data + 4, (uint32_t)size - CHUNK_HEADER_SIZE);
+  PutLE32(data + TAG_SIZE, (uint32_t)size - CHUNK_HEADER_SIZE);
   assert(size == (uint32_t)size);
-  PutLE32(data + 8, mktag('W', 'E', 'B', 'P'));
+  PutLE32(data + TAG_SIZE + CHUNK_SIZE_BYTES, mktag('W', 'E', 'B', 'P'));
 
   // Chunks.
   dst = data + RIFF_HEADER_SIZE;
diff --git a/src/mux/muxi.h b/src/mux/muxi.h
index cbb3b33e..4a52c480 100644
--- a/src/mux/muxi.h
+++ b/src/mux/muxi.h
@@ -87,6 +87,7 @@ typedef enum {
 // Maximum chunk payload (data) size such that adding the header and padding
 // won't overflow an uint32.
 #define MAX_CHUNK_PAYLOAD (~0U - CHUNK_HEADER_SIZE - 1)
+#define CHUNK_SIZE_BYTES 4
 
 #define NIL_TAG 0x00000000u  // To signal void chunk.
 
diff --git a/src/mux/muxread.c b/src/mux/muxread.c
index fdc8c847..d62fb300 100644
--- a/src/mux/muxread.c
+++ b/src/mux/muxread.c
@@ -217,9 +217,7 @@ WebPMuxError WebPMuxGetFeatures(const WebPMux* const mux, uint32_t* flags) {
     return err;
   }
 
-  // TODO(urvang): Add a '#define CHUNK_SIZE_BYTES 4' and use it instead of
-  // hard-coded value of 4 everywhere.
-  if (data.size_ < 4) return WEBP_MUX_BAD_DATA;
+  if (data.size_ < CHUNK_SIZE_BYTES) return WEBP_MUX_BAD_DATA;
 
   // All OK. Fill up flags.
   *flags = GetLE32(data.bytes_);
@@ -231,8 +229,9 @@ WebPMuxError WebPMuxGetImage(const WebPMux* const mux,
   WebPMuxError err;
   WebPMuxImage* wpi = NULL;
 
-  if (mux == NULL || (image == NULL && alpha == NULL))
+  if (mux == NULL || (image == NULL && alpha == NULL)) {
     return WEBP_MUX_INVALID_ARGUMENT;
+  }
 
   err = ValidateForImage(mux);
   if (err != WEBP_MUX_OK) return err;