diff --git a/lib/linter.js b/lib/linter.js
index 8f1520aafb4..595ce77b878 100755
--- a/lib/linter.js
+++ b/lib/linter.js
@@ -697,6 +697,8 @@ const BASE_TRAVERSAL_CONTEXT = Object.freeze(
     )
 );
 
+const lastSourceCodes = new WeakMap();
+
 //------------------------------------------------------------------------------
 // Public Interface
 //------------------------------------------------------------------------------
@@ -708,7 +710,7 @@ const BASE_TRAVERSAL_CONTEXT = Object.freeze(
 module.exports = class Linter {
 
     constructor() {
-        this.sourceCode = null;
+        lastSourceCodes.set(this, null);
         this.version = pkg.version;
 
         this.rules = new Rules();
@@ -754,11 +756,11 @@ module.exports = class Linter {
         const filename = typeof providedFilename === "string" ? providedFilename : "<input>";
 
         if (typeof textOrSourceCode === "string") {
-            this.sourceCode = null;
+            lastSourceCodes.set(this, null);
             text = textOrSourceCode;
         } else {
-            this.sourceCode = textOrSourceCode;
-            text = this.sourceCode.text;
+            lastSourceCodes.set(this, textOrSourceCode);
+            text = textOrSourceCode.text;
         }
 
         // search and apply "eslint-env *".
@@ -777,13 +779,13 @@ module.exports = class Linter {
         // process initial config to make it safe to extend
         config = prepareConfig(config, this.environments);
 
-        if (this.sourceCode) {
+        if (lastSourceCodes.get(this)) {
             parserServices = {};
         } else {
 
             // there's no input, just exit here
             if (text.trim().length === 0) {
-                this.sourceCode = new SourceCode(text, blankScriptAST);
+                lastSourceCodes.set(this, new SourceCode(text, blankScriptAST));
                 return [];
             }
 
@@ -799,11 +801,11 @@ module.exports = class Linter {
             }
 
             parserServices = parseResult.services;
-            this.sourceCode = new SourceCode(text, parseResult.ast);
+            lastSourceCodes.set(this, new SourceCode(text, parseResult.ast));
         }
 
         const problems = [];
-        const sourceCode = this.sourceCode;
+        const sourceCode = lastSourceCodes.get(this);
         let disableDirectives;
 
         // parse global comments and modify config
@@ -1005,7 +1007,7 @@ module.exports = class Linter {
      * @returns {SourceCode} The SourceCode object.
      */
     getSourceCode() {
-        return this.sourceCode;
+        return lastSourceCodes.get(this);
     }
 
     /**