diff --git a/lib/espree.js b/lib/espree.js
index 107affd1..770d9105 100644
--- a/lib/espree.js
+++ b/lib/espree.js
@@ -10,12 +10,14 @@ const STATE = Symbol("espree's internal state");
 const ESPRIMA_FINISH_NODE = Symbol("espree's esprimaFinishNode");
 const tokTypes = Object.assign({}, acorn.tokTypes, jsx.tokTypes);
 
+
 /**
  * Normalize ECMAScript version from the initial config
  * @param {number} ecmaVersion ECMAScript version from the initial config
+ * @throws {Error} throws an error if the ecmaVersion is invalid.
  * @returns {number} normalized ECMAScript version
  */
-function normalizeEcmaVersion(ecmaVersion) {
+function validateEcmaVersion(ecmaVersion = DEFAULT_ECMA_VERSION) {
     if (typeof ecmaVersion === "number") {
         let version = ecmaVersion;
 
@@ -36,11 +38,39 @@ function normalizeEcmaVersion(ecmaVersion) {
                 return version;
 
             default:
-                throw new Error("Invalid ecmaVersion.");
         }
-    } else {
-        return DEFAULT_ECMA_VERSION;
     }
+
+    throw new Error("Invalid ecmaVersion.");
+}
+
+/**
+ * Normalize sourceType from the initial config
+ * @param {string} sourceType to normalize
+ * @throws {Error} throw an error if sourceType is invalid
+ * @returns {string} normalized sourceType
+ */
+function validateSourceType(sourceType = "script") {
+    if (sourceType === "script" || sourceType === "module") {
+        return sourceType;
+    }
+    throw new Error("Invalid sourceType.");
+}
+
+/**
+ * Normalize parserOptions
+ * @param {Object} options the parser options to normalize
+ * @throws {Error} throw an error if found invalid option.
+ * @returns {Object} normalized options
+ */
+function validate(options) {
+    const ecmaVersion = validateEcmaVersion(options.ecmaVersion);
+    const sourceType = validateSourceType(options.sourceType);
+
+    if (options.sourceType === "module" && options.ecmaVersion < 6) {
+        throw new Error("sourceType 'module' is not supported when ecmaVersion < 6!");
+    }
+    return Object.assign({}, options, { ecmaVersion, sourceType });
 }
 
 /**
@@ -77,17 +107,17 @@ function convertAcornCommentToEsprimaComment(block, text, start, end, startLoc,
 }
 
 module.exports = () => Parser => class Espree extends Parser {
-    constructor(options, code) {
-        if (typeof options !== "object" || options === null) {
-            options = {};
+    constructor(opts, code) {
+        if (typeof opts !== "object" || opts === null) {
+            opts = {};
         }
         if (typeof code !== "string" && !(code instanceof String)) {
             code = String(code);
         }
+        const options = validate(opts);
 
         const ecmaFeatures = options.ecmaFeatures || {};
-        const ecmaVersion = normalizeEcmaVersion(options.ecmaVersion);
-        const isModule = options.sourceType === "module";
+        const ecmaVersion = validateEcmaVersion(options.ecmaVersion);
         const tokenTranslator =
             options.tokens === true
                 ? new TokenTranslator(tokTypes, code)
@@ -95,8 +125,8 @@ module.exports = () => Parser => class Espree extends Parser {
 
         // Initialize acorn parser.
         super({
-            ecmaVersion: isModule ? Math.max(6, ecmaVersion) : ecmaVersion,
-            sourceType: isModule ? "module" : "script",
+            ecmaVersion,
+            sourceType: options.sourceType,
             ranges: options.range === true,
             locations: options.loc === true,
 
diff --git a/tests/lib/ecma-version.js b/tests/lib/ecma-version.js
index bd533d4e..7b02cd7c 100644
--- a/tests/lib/ecma-version.js
+++ b/tests/lib/ecma-version.js
@@ -141,6 +141,30 @@ describe("ecmaVersion", () => {
             }, /Invalid ecmaVersion/);
         });
 
+        it("Should throw error using invalid year", () => {
+            assert.throws(() => {
+                espree.parse(
+                    "let foo = bar;", {
+                        ecmaVersion: "2015",
+                        comment: true,
+                        tokens: true,
+                        range: true,
+                        loc: true
+                    }
+                );
+            }, /Invalid ecmaVersion/);
+        });
+
+        it("Should throw error when using module in pre-ES6", () => {
+            assert.throws(() => {
+                espree.parse(
+                    "let foo = bar;", {
+                        ecmaVersion: 5,
+                        sourceType: "module"
+                    }
+                );
+            }, /sourceType 'module' is not supported when ecmaVersion < 6!/);
+        });
     });
 
 });