diff --git a/src/cmd/exclude.rs b/src/cmd/exclude.rs
index e16abbc3f..72ee3f5ee 100644
--- a/src/cmd/exclude.rs
+++ b/src/cmd/exclude.rs
@@ -49,11 +49,9 @@ use crate::{
     config::{Config, Delimiter},
     index::Indexed,
     select::{SelectColumns, Selection},
-    util, CliResult,
+    util, CliResult, util::ByteString
 };
 
-type ByteString = Vec<u8>;
-
 #[derive(Deserialize)]
 struct Args {
     arg_columns1:     SelectColumns,
diff --git a/src/cmd/fill.rs b/src/cmd/fill.rs
index 827793dc7..9579ba311 100644
--- a/src/cmd/fill.rs
+++ b/src/cmd/fill.rs
@@ -59,10 +59,11 @@ use serde::Deserialize;
 use crate::{
     config::{Config, Delimiter},
     select::{SelectColumns, Selection},
-    util, CliResult,
+    util,
+    util::ByteString,
+    CliResult,
 };
 
-type ByteString = Vec<u8>;
 type BoxedWriter = csv::Writer<Box<dyn io::Write + 'static>>;
 type BoxedReader = csv::Reader<Box<dyn io::Read + Send + 'static>>;
 
diff --git a/src/cmd/frequency.rs b/src/cmd/frequency.rs
index eab9c9a4e..125867704 100644
--- a/src/cmd/frequency.rs
+++ b/src/cmd/frequency.rs
@@ -60,7 +60,9 @@ use crate::{
     config::{Config, Delimiter},
     index::Indexed,
     select::{SelectColumns, Selection},
-    util, CliResult,
+    util,
+    util::ByteString,
+    CliResult,
 };
 
 #[derive(Clone, Deserialize)]
@@ -109,7 +111,6 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
     Ok(())
 }
 
-type ByteString = Vec<u8>;
 type Headers = csv::ByteRecord;
 type FTable = Frequencies<Vec<u8>>;
 type FTables = Vec<Frequencies<Vec<u8>>>;