diff --git a/src/ser/flavors.rs b/src/ser/flavors.rs
index ce414e4..b55af1a 100644
--- a/src/ser/flavors.rs
+++ b/src/ser/flavors.rs
@@ -429,13 +429,12 @@ pub mod crc {
     use crc::Width;
 
     use super::Flavor;
-    use super::IndexMut;
     use crate::Result;
 
     /// Manages CRC modifications as a flavor.
     pub struct CrcModifier<'a, B, W>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
         W: Width,
     {
         flav: B,
@@ -444,7 +443,7 @@ pub mod crc {
 
     impl<'a, B, W> CrcModifier<'a, B, W>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
         W: Width,
     {
         /// Create a new Crc modifier Flavor.
@@ -463,7 +462,7 @@ pub mod crc {
 
     impl<'a, B> Flavor for CrcModifier<'a, B, u8>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
     {
         type Output = <B as Flavor>::Output;
 
@@ -482,7 +481,7 @@ pub mod crc {
 
     impl<'a, B> Flavor for CrcModifier<'a, B, u16>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
     {
         type Output = <B as Flavor>::Output;
 
@@ -501,7 +500,7 @@ pub mod crc {
 
     impl<'a, B> Flavor for CrcModifier<'a, B, u32>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
     {
         type Output = <B as Flavor>::Output;
 
@@ -520,7 +519,7 @@ pub mod crc {
 
     impl<'a, B> Flavor for CrcModifier<'a, B, u64>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
     {
         type Output = <B as Flavor>::Output;
 
@@ -539,7 +538,7 @@ pub mod crc {
 
     impl<'a, B> Flavor for CrcModifier<'a, B, u128>
     where
-        B: Flavor + IndexMut<usize, Output = u8>,
+        B: Flavor,
     {
         type Output = <B as Flavor>::Output;