diff --git a/packages/babel-generator/src/whitespace.js b/packages/babel-generator/src/whitespace.js
index 05816b1b73..35ba9e691f 100644
--- a/packages/babel-generator/src/whitespace.js
+++ b/packages/babel-generator/src/whitespace.js
@@ -1,18 +1,3 @@
-/**
- * Returns `i`th number from `base`, continuing from 0 when `max` is reached.
- * Useful for shifting `for` loop by a fixed number but going over all items.
- */
-
-function getLookupIndex(i: number, base: number, max: number): number {
-  i += base;
-
-  if (i >= max) {
-    i -= max;
-  }
-
-  return i;
-}
-
 /**
  * Get whitespace around tokens.
  */
@@ -21,16 +6,6 @@ export default class Whitespace {
   constructor(tokens) {
     this.tokens = tokens;
     this.used   = {};
-
-    // Profiling this code shows that while generator passes over it, indexes
-    // returned by `getNewlinesBefore` and `getNewlinesAfter` are always increasing.
-
-    // We use this implementation detail for an optimization: instead of always
-    // starting to look from `this.tokens[0]`, we will start `for` loops from the
-    // previous successful match. We will enumerate all tokens—but the common
-    // case will be much faster.
-
-    this._lastFoundIndex = 0;
   }
 
   /**
@@ -42,19 +17,11 @@ export default class Whitespace {
     let endToken;
     let tokens = this.tokens;
 
-    for (let j = 0; j < tokens.length; j++) {
-      // optimize for forward traversal by shifting for loop index
-      let i = getLookupIndex(j, this._lastFoundIndex, this.tokens.length);
-      let token = tokens[i];
-
-      // this is the token this node starts with
-      if (node.start === token.start) {
-        startToken = tokens[i - 1];
-        endToken = token;
-
-        this._lastFoundIndex = i;
-        break;
-      }
+    let index = this.findToken(token => token.start - node.start, 0, tokens.length);
+    if (typeof index === "number") {
+      while (index && node.start === tokens[index - 1].start) --index;
+      startToken = tokens[index - 1];
+      endToken = tokens[index];
     }
 
     return this.getNewlinesBetween(startToken, endToken);
@@ -69,20 +36,12 @@ export default class Whitespace {
     let endToken;
     let tokens = this.tokens;
 
-    for (let j = 0; j < tokens.length; j++) {
-      // optimize for forward traversal by shifting for loop index
-      let i = getLookupIndex(j, this._lastFoundIndex, this.tokens.length);
-      let token = tokens[i];
-
-      // this is the token this node ends with
-      if (node.end === token.end) {
-        startToken = token;
-        endToken = tokens[i + 1];
-        if (endToken.type.label === ",") endToken = tokens[i + 2];
-
-        this._lastFoundIndex = i;
-        break;
-      }
+    let index = this.findToken(token => token.end - node.end, 0, tokens.length);
+    if (typeof index === "number") {
+      while (index && node.end === tokens[index - 1].end) --index;
+      startToken = tokens[index];
+      endToken = tokens[index + 1];
+      if (endToken.type.label === ",") endToken = tokens[index + 2];
     }
 
     if (endToken && endToken.type.label === "eof") {
@@ -98,6 +57,18 @@ export default class Whitespace {
     }
   }
 
+  findToken(test, start, end) {
+    const middle = (start + end) >>> 1;
+    const match = test(this.tokens[middle]);
+    if (match < 0 && end > middle) {
+      return this.findToken(test, middle + 1, end);
+    } else if (match > 0 && start < middle) {
+      return this.findToken(test, start, middle);
+    } else if (match === 0) {
+      return middle;
+    }
+  }
+
   /**
    * Count all the newlines between two tokens.
    */