diff --git a/actix-http/benches/content-length.rs b/actix-http/benches/content-length.rs
index 150f48a2c..b001b3931 100644
--- a/actix-http/benches/content-length.rs
+++ b/actix-http/benches/content-length.rs
@@ -67,7 +67,7 @@ mod _new {
             bytes.put_u8(DIGITS_START + d100);
             bytes.put_u8(DIGITS_START + d10);
             bytes.put_u8(DIGITS_START + d1);
-        } else if n < 10000 {
+        } else if n < 10_000 {
             let n = n as u16;
 
             let d1000 = (n / 1000) as u8;
@@ -75,6 +75,36 @@ mod _new {
             let d10 = ((n / 10) % 10) as u8;
             let d1 = (n % 10) as u8;
 
+            bytes.put_u8(DIGITS_START + d1000);
+            bytes.put_u8(DIGITS_START + d100);
+            bytes.put_u8(DIGITS_START + d10);
+            bytes.put_u8(DIGITS_START + d1);
+        } else if n < 100_000 {
+            let n = n as u32;
+
+            let d10000 = (n / 10000) as u8;
+            let d1000 = ((n / 1000) % 10) as u8;
+            let d100 = ((n / 100) % 10) as u8;
+            let d10 = ((n / 10) % 10) as u8;
+            let d1 = (n % 10) as u8;
+
+            bytes.put_u8(DIGITS_START + d10000);
+            bytes.put_u8(DIGITS_START + d1000);
+            bytes.put_u8(DIGITS_START + d100);
+            bytes.put_u8(DIGITS_START + d10);
+            bytes.put_u8(DIGITS_START + d1);
+        } else if n < 1_000_000 {
+            let n = n as u32;
+
+            let d100000 = (n / 100000) as u8;
+            let d10000 = ((n / 10000) % 10) as u8;
+            let d1000 = ((n / 1000) % 10) as u8;
+            let d100 = ((n / 100) % 10) as u8;
+            let d10 = ((n / 10) % 10) as u8;
+            let d1 = (n % 10) as u8;
+
+            bytes.put_u8(DIGITS_START + d100000);
+            bytes.put_u8(DIGITS_START + d10000);
             bytes.put_u8(DIGITS_START + d1000);
             bytes.put_u8(DIGITS_START + d100);
             bytes.put_u8(DIGITS_START + d10);
diff --git a/actix-http/src/helpers.rs b/actix-http/src/helpers.rs
index cba21ed0c..6599f6a32 100644
--- a/actix-http/src/helpers.rs
+++ b/actix-http/src/helpers.rs
@@ -88,7 +88,7 @@ pub fn write_content_length(n: usize, bytes: &mut BytesMut) {
         bytes.put_u8(DIGITS_START + d100);
         bytes.put_u8(DIGITS_START + d10);
         bytes.put_u8(DIGITS_START + d1);
-    } else if n < 10000 {
+    } else if n < 10_000 {
         let n = n as u16;
 
         let d1000 = (n / 1000) as u8;
@@ -96,6 +96,36 @@ pub fn write_content_length(n: usize, bytes: &mut BytesMut) {
         let d10 = ((n / 10) % 10) as u8;
         let d1 = (n % 10) as u8;
 
+        bytes.put_u8(DIGITS_START + d1000);
+        bytes.put_u8(DIGITS_START + d100);
+        bytes.put_u8(DIGITS_START + d10);
+        bytes.put_u8(DIGITS_START + d1);
+    } else if n < 100_000 {
+        let n = n as u32;
+
+        let d10000 = (n / 10000) as u8;
+        let d1000 = ((n / 1000) % 10) as u8;
+        let d100 = ((n / 100) % 10) as u8;
+        let d10 = ((n / 10) % 10) as u8;
+        let d1 = (n % 10) as u8;
+
+        bytes.put_u8(DIGITS_START + d10000);
+        bytes.put_u8(DIGITS_START + d1000);
+        bytes.put_u8(DIGITS_START + d100);
+        bytes.put_u8(DIGITS_START + d10);
+        bytes.put_u8(DIGITS_START + d1);
+    } else if n < 1_000_000 {
+        let n = n as u32;
+
+        let d100000 = (n / 100000) as u8;
+        let d10000 = ((n / 10000) % 10) as u8;
+        let d1000 = ((n / 1000) % 10) as u8;
+        let d100 = ((n / 100) % 10) as u8;
+        let d10 = ((n / 10) % 10) as u8;
+        let d1 = (n % 10) as u8;
+
+        bytes.put_u8(DIGITS_START + d100000);
+        bytes.put_u8(DIGITS_START + d10000);
         bytes.put_u8(DIGITS_START + d1000);
         bytes.put_u8(DIGITS_START + d100);
         bytes.put_u8(DIGITS_START + d10);
@@ -109,7 +139,7 @@ pub fn write_content_length(n: usize, bytes: &mut BytesMut) {
 
 pub(crate) fn write_usize(n: usize, bytes: &mut BytesMut) {
     let mut n = n;
-    
+
     // 20 chars is max length of a usize (2^64)
     // digits will be added to the buffer from lsd to msd
     let mut buf = BytesMut::with_capacity(20);
@@ -126,7 +156,7 @@ pub(crate) fn write_usize(n: usize, bytes: &mut BytesMut) {
 
     // put msd to result buffer
     bytes.put_u8(DIGITS_START + (n as u8));
-    
+
     // put, in reverse (msd to lsd), remaining digits to buffer
     for i in (0..buf.len()).rev() {
         bytes.put_u8(buf[i]);
@@ -195,11 +225,17 @@ mod tests {
         write_content_length(5909, &mut bytes);
         assert_eq!(bytes.split().freeze(), b"\r\ncontent-length: 5909\r\n"[..]);
         bytes.reserve(50);
+        write_content_length(9999, &mut bytes);
+        assert_eq!(bytes.split().freeze(), b"\r\ncontent-length: 9999\r\n"[..]);
+        bytes.reserve(50);
         write_content_length(10001, &mut bytes);
         assert_eq!(bytes.split().freeze(), b"\r\ncontent-length: 10001\r\n"[..]);
         bytes.reserve(50);
         write_content_length(59094, &mut bytes);
         assert_eq!(bytes.split().freeze(), b"\r\ncontent-length: 59094\r\n"[..]);
+        bytes.reserve(50);
+        write_content_length(99999, &mut bytes);
+        assert_eq!(bytes.split().freeze(), b"\r\ncontent-length: 99999\r\n"[..]);
 
         bytes.reserve(50);
         write_content_length(590947, &mut bytes);
@@ -208,6 +244,12 @@ mod tests {
             b"\r\ncontent-length: 590947\r\n"[..]
         );
         bytes.reserve(50);
+        write_content_length(999999, &mut bytes);
+        assert_eq!(
+            bytes.split().freeze(),
+            b"\r\ncontent-length: 999999\r\n"[..]
+        );
+        bytes.reserve(50);
         write_content_length(5909471, &mut bytes);
         assert_eq!(
             bytes.split().freeze(),
@@ -219,5 +261,11 @@ mod tests {
             bytes.split().freeze(),
             b"\r\ncontent-length: 59094718\r\n"[..]
         );
+        bytes.reserve(50);
+        write_content_length(4294973728, &mut bytes);
+        assert_eq!(
+            bytes.split().freeze(),
+            b"\r\ncontent-length: 4294973728\r\n"[..]
+        );
     }
 }