diff --git a/lib/chai/utils/proxify.js b/lib/chai/utils/proxify.js
index fd986d015..51e0e63e7 100644
--- a/lib/chai/utils/proxify.js
+++ b/lib/chai/utils/proxify.js
@@ -112,10 +112,12 @@ function stringDistance(strA, strB, memo) {
     if (strA.length === 0 || strB.length === 0) {
       memo[strA.length][strB.length] = Math.max(strA.length, strB.length);
     } else {
+      var sliceA = strA.slice(0, -1);
+      var sliceB = strB.slice(0, -1);
       memo[strA.length][strB.length] = Math.min(
-        stringDistance(strA.slice(0, -1), strB, memo) + 1,
-        stringDistance(strA, strB.slice(0, -1), memo) + 1,
-        stringDistance(strA.slice(0, -1), strB.slice(0, -1), memo) +
+        stringDistance(sliceA, strB, memo) + 1,
+        stringDistance(strA, sliceB, memo) + 1,
+        stringDistance(sliceA, sliceB, memo) +
           (strA.slice(-1) === strB.slice(-1) ? 0 : 1)
       );
     }