diff --git a/lib/fetch/dataURL.js b/lib/fetch/dataURL.js
index 12fa1abbb93..d7a638866a3 100644
--- a/lib/fetch/dataURL.js
+++ b/lib/fetch/dataURL.js
@@ -604,14 +604,18 @@ function isHTTPWhiteSpace (char) {
  * @param {boolean} [trailing=true]
  */
 function removeHTTPWhitespace (str, leading = true, trailing = true) {
-  let i = 0; let j = str.length
+  let lead = 0
+  let trail = str.length - 1
+
   if (leading) {
-    while (j > i && isHTTPWhiteSpace(str.charCodeAt(i))) --i
+    while (lead < str.length && isHTTPWhiteSpace(str.charCodeAt(lead))) lead++
   }
+
   if (trailing) {
-    while (j > i && isHTTPWhiteSpace(str.charCodeAt(j - 1))) --j
+    while (trail > 0 && isHTTPWhiteSpace(str.charCodeAt(trail))) trail--
   }
-  return i === 0 && j === str.length ? str : str.substring(i, j)
+
+  return lead === 0 && trail === str.length - 1 ? str : str.slice(lead, trail + 1)
 }
 
 /**
@@ -630,14 +634,18 @@ function isASCIIWhitespace (char) {
  * @param {boolean} [trailing=true]
  */
 function removeASCIIWhitespace (str, leading = true, trailing = true) {
-  let i = 0; let j = str.length
+  let lead = 0
+  let trail = str.length - 1
+
   if (leading) {
-    while (j > i && isASCIIWhitespace(str.charCodeAt(i))) --i
+    while (lead < str.length && isASCIIWhitespace(str.charCodeAt(lead))) lead++
   }
+
   if (trailing) {
-    while (j > i && isASCIIWhitespace(str.charCodeAt(j - 1))) --j
+    while (trail > 0 && isASCIIWhitespace(str.charCodeAt(trail))) trail--
   }
-  return i === 0 && j === str.length ? str : str.substring(i, j)
+
+  return lead === 0 && trail === str.length - 1 ? str : str.slice(lead, trail + 1)
 }
 
 module.exports = {