diff --git a/lib/linter/linter.js b/lib/linter/linter.js
index 82df6a55a956..815ef9f2a16a 100644
--- a/lib/linter/linter.js
+++ b/lib/linter/linter.js
@@ -441,10 +441,6 @@ function normalizeEcmaVersion(parser, ecmaVersion) {
 
     // RuleTester always wraps parser, parser.$parser is the original parser object
     if ((parser.$parser || parser) === espree) {
-        if (ecmaVersion === void 0) {
-            return DEFAULT_ECMA_VERSION;
-        }
-
         if (ecmaVersion === "latest") {
             return espree.latestEcmaVersion;
         }
diff --git a/tests/lib/linter/linter.js b/tests/lib/linter/linter.js
index 15d310c9ab93..ed7213defcab 100644
--- a/tests/lib/linter/linter.js
+++ b/tests/lib/linter/linter.js
@@ -3501,19 +3501,6 @@ var a = "test2";
                 assert.strictEqual(messages.length, 1);
             });
 
-            it("the default ECMAScript version is 5", () => {
-                let ecmaVersion = null;
-                const config = { rules: { "ecma-version": 2 } };
-
-                linter.defineRule("ecma-version", context => ({
-                    Program() {
-                        ecmaVersion = context.parserOptions.ecmaVersion;
-                    }
-                }));
-                linter.verify("", config);
-                assert.strictEqual(ecmaVersion, 5);
-            });
-
             it("supports ECMAScript version 'latest'", () => {
                 const messages = linter.verify("let x = 5 ** 7;", {
                     parserOptions: { ecmaVersion: "latest" }
diff --git a/tests/lib/rule-tester/rule-tester.js b/tests/lib/rule-tester/rule-tester.js
index 705ba2efe52b..8e6f8d9f2357 100644
--- a/tests/lib/rule-tester/rule-tester.js
+++ b/tests/lib/rule-tester/rule-tester.js
@@ -809,21 +809,21 @@ describe("RuleTester", () => {
             invalid: [
                 {
                     code: "",
-                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "number", ecmaVersion: "5" } }]
+                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "undefined", ecmaVersion: "undefined" } }]
                 },
                 {
                     code: "",
-                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "number", ecmaVersion: "5" } }],
+                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "undefined", ecmaVersion: "undefined" } }],
                     parserOptions: {}
                 },
                 {
                     code: "<div/>",
-                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "number", ecmaVersion: "5" } }],
+                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "undefined", ecmaVersion: "undefined" } }],
                     parserOptions: { ecmaFeatures: { jsx: true } }
                 },
                 {
                     code: "",
-                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "number", ecmaVersion: "5" } }],
+                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "undefined", ecmaVersion: "undefined" } }],
                     parser: require.resolve("espree")
                 },
                 {
@@ -838,12 +838,12 @@ describe("RuleTester", () => {
                 },
                 {
                     code: "",
-                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "number", ecmaVersion: "5" } }],
+                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "undefined", ecmaVersion: "undefined" } }],
                     env: { browser: true }
                 },
                 {
                     code: "",
-                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "number", ecmaVersion: "5" } }],
+                    errors: [{ messageId: "ecmaVersionMessage", data: { type: "undefined", ecmaVersion: "undefined" } }],
                     env: { es6: false }
                 },
                 {