diff --git a/src/header/common/cache_control.rs b/src/header/common/cache_control.rs
index 68e8546f13..0629aea2e0 100644
--- a/src/header/common/cache_control.rs
+++ b/src/header/common/cache_control.rs
@@ -1,7 +1,7 @@
 use std::fmt;
 use std::str::FromStr;
 use header::{Header, HeaderFormat};
-use header::parsing::{from_one_comma_delimited, fmt_comma_delimited};
+use header::parsing::{from_comma_delimited, fmt_comma_delimited};
 
 /// `Cache-Control` header, defined in [RFC7234](https://tools.ietf.org/html/rfc7234#section-5.2)
 ///
@@ -55,10 +55,7 @@ impl Header for CacheControl {
     }
 
     fn parse_header(raw: &[Vec<u8>]) -> ::Result<CacheControl> {
-        let directives = raw.iter()
-            .filter_map(|line| from_one_comma_delimited(&line[..]).ok())
-            .collect::<Vec<Vec<CacheDirective>>>()
-            .concat();
+        let directives = try!(from_comma_delimited(raw));
         if !directives.is_empty() {
             Ok(CacheControl(directives))
         } else {
diff --git a/src/header/common/content_length.rs b/src/header/common/content_length.rs
index 0f74d861c4..8c9707aeaa 100644
--- a/src/header/common/content_length.rs
+++ b/src/header/common/content_length.rs
@@ -79,7 +79,16 @@ __hyper__tm!(ContentLength, tests {
     test_header!(test1, vec![b"3495"], Some(HeaderField(3495)));
 
     test_header!(test_invalid, vec![b"34v95"], None);
-    test_header!(test_duplicates, vec![b"5", b"5"], Some(HeaderField(5)));
+
+    // Can't use the test_header macro because "5, 5" gets cleaned to "5".
+    #[test]
+    fn test_duplicates() {
+        let parsed = HeaderField::parse_header(&[b"5"[..].into(),
+                                                 b"5"[..].into()]).unwrap();
+        assert_eq!(parsed, HeaderField(5));
+        assert_eq!(format!("{}", parsed), "5");
+    }
+
     test_header!(test_duplicates_vary, vec![b"5", b"6", b"5"], None);
 });
 
diff --git a/src/header/common/mod.rs b/src/header/common/mod.rs
index 090f02370f..56f82603d3 100644
--- a/src/header/common/mod.rs
+++ b/src/header/common/mod.rs
@@ -156,8 +156,15 @@ macro_rules! test_header {
             assert_eq!(val.ok(), typed);
             // Test formatting
             if typed.is_some() {
-                let res: &str = str::from_utf8($raw[0]).unwrap();
-                assert_eq!(format!("{}", typed.unwrap()), res);
+                let raw = &($raw)[..];
+                let mut iter = raw.iter().map(|b|str::from_utf8(&b[..]).unwrap());
+                let mut joined = String::new();
+                joined.push_str(iter.next().unwrap());
+                for s in iter {
+                    joined.push_str(", ");
+                    joined.push_str(s);
+                }
+                assert_eq!(format!("{}", typed.unwrap()), joined);
             }
         }
     }
diff --git a/src/header/common/range.rs b/src/header/common/range.rs
index 8b09860b32..49c2d4b522 100644
--- a/src/header/common/range.rs
+++ b/src/header/common/range.rs
@@ -2,7 +2,7 @@ use std::fmt::{self, Display};
 use std::str::FromStr;
 
 use header::{Header, HeaderFormat};
-use header::parsing::{from_one_raw_str, from_one_comma_delimited};
+use header::parsing::{from_one_raw_str, from_comma_delimited};
 
 /// `Range` header, defined in [RFC7233](https://tools.ietf.org/html/rfc7233#section-3.1)
 ///
@@ -130,7 +130,7 @@ impl FromStr for Range {
 
         match (iter.next(), iter.next()) {
             (Some("bytes"), Some(ranges)) => {
-                match from_one_comma_delimited(ranges.as_bytes()) {
+                match from_comma_delimited(&[ranges]) {
                     Ok(ranges) => {
                         if ranges.is_empty() {
                             return Err(::Error::Header);
diff --git a/src/header/common/transfer_encoding.rs b/src/header/common/transfer_encoding.rs
index c8eaa7bdad..13ae54a34c 100644
--- a/src/header/common/transfer_encoding.rs
+++ b/src/header/common/transfer_encoding.rs
@@ -38,6 +38,13 @@ header! {
             Some(HeaderField(
                 vec![Encoding::Gzip, Encoding::Chunked]
                 )));
+        // Issue: #683
+        test_header!(
+            test2,
+            vec![b"chunked", b"chunked"],
+            Some(HeaderField(
+                vec![Encoding::Chunked, Encoding::Chunked]
+            )));
 
     }
 }
diff --git a/src/header/parsing.rs b/src/header/parsing.rs
index 49029b58eb..bbb158b0eb 100644
--- a/src/header/parsing.rs
+++ b/src/header/parsing.rs
@@ -23,24 +23,18 @@ pub fn from_raw_str<T: str::FromStr>(raw: &[u8]) -> ::Result<T> {
 
 /// Reads a comma-delimited raw header into a Vec.
 #[inline]
-pub fn from_comma_delimited<T: str::FromStr>(raw: &[Vec<u8>]) -> ::Result<Vec<T>> {
-    if raw.len() != 1 {
-        return Err(::Error::Header);
+pub fn from_comma_delimited<T: str::FromStr, S: AsRef<[u8]>>(raw: &[S]) -> ::Result<Vec<T>> {
+    let mut result = Vec::new();
+    for s in raw {
+        let s = try!(str::from_utf8(s.as_ref()));
+        result.extend(s.split(',')
+                      .filter_map(|x| match x.trim() {
+                          "" => None,
+                          y => Some(y)
+                      })
+                      .filter_map(|x| x.parse().ok()))
     }
-    // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
-    from_one_comma_delimited(& unsafe { raw.get_unchecked(0) }[..])
-}
-
-/// Reads a comma-delimited raw string into a Vec.
-pub fn from_one_comma_delimited<T: str::FromStr>(raw: &[u8]) -> ::Result<Vec<T>> {
-    let s = try!(str::from_utf8(raw));
-    Ok(s.split(',')
-        .filter_map(|x| match x.trim() {
-            "" => None,
-            y => Some(y)
-        })
-        .filter_map(|x| x.parse().ok())
-        .collect())
+    Ok(result)
 }
 
 /// Format an array into a comma-delimited string.