diff --git a/lib/6to5/generation/whitespace.js b/lib/6to5/generation/whitespace.js
index 637b155c3a..aa0993bc2a 100644
--- a/lib/6to5/generation/whitespace.js
+++ b/lib/6to5/generation/whitespace.js
@@ -1,7 +1,6 @@
 module.exports = Whitespace;
 
 var _    = require("lodash");
-var util = require("../util");
 
 /**
  * Returns `i`th number from `base`, continuing from 0 when `max` is reached.
@@ -23,7 +22,7 @@ function getLookupIndex(i, base, max) {
 
 function Whitespace(tokens, comments) {
   this.tokens = _.sortBy(tokens.concat(comments), "start");
-  this.used   = [];
+  this.used   = {};
 
   // Profiling this code shows that while generator passes over it, indexes
   // returned by `getNewlinesBefore` and `getNewlinesAfter` are always increasing.
@@ -97,6 +96,14 @@ Whitespace.prototype.getNewlinesAfter = function (node) {
 Whitespace.prototype.getNewlinesBetween = function (startToken, endToken) {
   var start = startToken ? startToken.loc.end.line : 1;
   var end   = endToken.loc.start.line;
+  var lines = 0;
 
-  return util.mergeIntegerRange(this.used, start, end);
+  for (var line = start; line < end; line++) {
+    if (typeof this.used[line] === 'undefined') {
+      this.used[line] = true;
+      lines++;
+    }
+  }
+
+  return lines;
 };
\ No newline at end of file
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index c594f3e653..66af587e4f 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -204,84 +204,6 @@ exports.repeat = function (width, cha) {
   return result;
 };
 
-/**
- * Merges a range of integers defined by `start` and `end` into an existing
- * array of `ranges`, optimizing for common cases and attempting to keep them
- * sorted. Returns the count of integers that have been added to `ranges` during
- * the call.
- *
- * @example
- * > var ranges = [{ start: 1, end: 3}, { start: 8, end : 10 }];
- * > mergeIntegerRange(ranges, 6, 9);
- * 2
- * > ranges
- * [{ start: 1, end: 3}, { start: 6, end : 10 }];
- *
- * @param {Array} ranges An array of ranges that function will mutate
- * @param {Number} start Beginning of range being added
- * @param {Number} end End of range being added
- * @returns {Number} pointsAdded How many new integers have been added
- */
-exports.mergeIntegerRange = function (ranges, start, end) {
-  var pointsAdded = 0;
-  var insertIndex;
-  var rangeIndex;
-  var point;
-  var range;
-  var matchingRange;
-  var rangeImmediatelyToLeft;
-  var rangeImmediatelyToRight;
-
-  for (point = start; point < end; point++) {
-    matchingRange = null;
-    rangeImmediatelyToLeft = null;
-    rangeImmediatelyToRight = null;
-    insertIndex = ranges.length;
-
-    for (rangeIndex = 0; rangeIndex < ranges.length; rangeIndex++) {
-      range = ranges[rangeIndex];
-
-      if (point >= range.start && point <= range.end) {
-        matchingRange = range;
-        break;
-      }
-
-      if (point < range.start) {
-        insertIndex = rangeIndex;
-      }
-
-      if (point === range.end + 1) {
-        rangeImmediatelyToLeft = range;
-      }
-
-      if (point === range.start - 1) {
-        rangeImmediatelyToRight = range;
-      }
-    }
-
-    if (matchingRange)
-      continue;
-
-    pointsAdded++;
-
-    if (rangeImmediatelyToLeft && rangeImmediatelyToRight) {
-      ranges.splice(ranges.indexOf(rangeImmediatelyToRight), 1);
-      rangeImmediatelyToLeft.end = rangeImmediatelyToRight.end;
-    } else if (rangeImmediatelyToLeft) {
-      rangeImmediatelyToLeft.end = point;
-    } else if (rangeImmediatelyToRight) {
-      rangeImmediatelyToRight.start = point;
-    } else {
-      ranges.splice(insertIndex, 0, {
-        start: point,
-        end: point
-      });
-    }
-  }
-
-  return pointsAdded;
-};
-
 exports.normaliseAst = function (ast, comments, tokens) {
   if (ast && ast.type === "Program") {
     return t.file(ast, comments || [], tokens || []);