diff --git a/src/chunks.rs b/src/chunks.rs
index b937bec..671bc7d 100644
--- a/src/chunks.rs
+++ b/src/chunks.rs
@@ -34,8 +34,8 @@ impl<T> WriteBWaveChunks for T where T: Write {
         self.write_u16::<LittleEndian>(format.block_alignment)?;
         self.write_u16::<LittleEndian>(format.bits_per_sample)?;
         if let Some(ext) = format.extended_format {
-            let cbSize = 24u16;
-            self.write_u16::<LittleEndian>(cbSize)?;
+            let cb_size = 24u16;
+            self.write_u16::<LittleEndian>(cb_size)?;
             self.write_u16::<LittleEndian>(ext.valid_bits_per_sample)?;
             self.write_u32::<LittleEndian>(ext.channel_mask)?;
             let uuid = ext.type_guid.as_bytes();