diff --git a/lib/shared.js b/lib/shared.js
index ffee555e..472a60e5 100644
--- a/lib/shared.js
+++ b/lib/shared.js
@@ -106,9 +106,11 @@ function filterTokens(params, type, callback) {
 }
 module.exports.filterTokens = filterTokens;
 
+var lastForEachLineParams = null;
+var lastForEachLineResult = null;
 // Calls the provided function for each line (with context)
 module.exports.forEachLine = function forEachLine(params, callback) {
-  if (!params.forEachLine) {
+  if (params !== lastForEachLineParams) {
     var lineMetadata = new Array(params.lines.length);
     var fenceStart = null;
     var inFence = false;
@@ -139,11 +141,12 @@ module.exports.forEachLine = function forEachLine(params, callback) {
         lineMetadata[i] += 8;
       }
     });
-    params.forEachLine = lineMetadata;
+    lastForEachLineParams = params;
+    lastForEachLineResult = lineMetadata;
   }
   // Invoke callback
   params.lines.forEach(function forLine(line, lineIndex) {
-    var metadata = params.forEachLine[lineIndex];
+    var metadata = lastForEachLineResult[lineIndex];
     callback(
       line,
       lineIndex,
@@ -179,9 +182,11 @@ module.exports.forEachHeading = function forEachHeading(params, callback) {
   });
 };
 
+var lastFlattenListsParams = null;
+var lastFlattenListsResult = null;
 // Returns (nested) lists as a flat array (in order)
 module.exports.flattenLists = function flattenLists(params) {
-  if (!params.flattenLists) {
+  if (lastFlattenListsParams !== params) {
     var lists = [];
     var stack = [];
     var current = null;
@@ -216,9 +221,10 @@ module.exports.flattenLists = function flattenLists(params) {
         lastWithMap = token;
       }
     });
-    params.flattenLists = lists;
+    lastFlattenListsParams = params;
+    lastFlattenListsResult = lists;
   }
-  return params.flattenLists;
+  return lastFlattenListsResult;
 };
 
 // Adds a generic error object via the onError callback