diff --git a/classes/range.js b/classes/range.js
index a791d912..988c6b7c 100644
--- a/classes/range.js
+++ b/classes/range.js
@@ -81,8 +81,8 @@ class Range {
 
     // memoize range parsing for performance.
     // this is a very hot path, and fully deterministic.
-    const memoOpts = Object.keys(this.options).join(',')
-    const memoKey = `parseRange:${memoOpts}:${range}`
+    const memoOpts = buildMemoKeyFromOptions(this.options)
+    const memoKey = memoOpts + ':' + range
     const cached = cache.get(memoKey)
     if (cached) {
       return cached
@@ -190,6 +190,15 @@ class Range {
     return false
   }
 }
+
+function buildMemoKeyFromOptions (options) {
+  return (
+      (options.loose ? 1 << 1 : 0)
+    | (options.includePrerelease ? 1 << 2 : 0)
+    | (options.rtl ? 1 << 3 : 0)
+  ) + ''
+}
+
 module.exports = Range
 
 const LRU = require('lru-cache')