diff --git a/eslint/babel-eslint-parser/index.js b/eslint/babel-eslint-parser/index.js
index f89554f130..3cf0b6537e 100644
--- a/eslint/babel-eslint-parser/index.js
+++ b/eslint/babel-eslint-parser/index.js
@@ -244,8 +244,13 @@ function monkeypatch() {
     // only visit if function parameters have types
     if (node.params) {
       for (var i = 0; i < node.params.length; i++) {
-        if (node.params[i].typeAnnotation) {
-          checkIdentifierOrVisit.call(this, node.params[i]);
+        var param = node.params[i];
+        if (param.typeAnnotation) {
+          checkIdentifierOrVisit.call(this, param);
+        } else if (t.isAssignmentPattern(param)) {
+          if (param.left.typeAnnotation) {
+            checkIdentifierOrVisit.call(this, param.left);
+          }
         }
       }
     }
diff --git a/eslint/babel-eslint-parser/test/non-regression.js b/eslint/babel-eslint-parser/test/non-regression.js
index 0dbea848c2..f24bad04e5 100644
--- a/eslint/babel-eslint-parser/test/non-regression.js
+++ b/eslint/babel-eslint-parser/test/non-regression.js
@@ -1309,4 +1309,23 @@ describe("verify", function () {
       [ ]
     )
   });
+
+  it("default param flow type no-unused-vars #184", function () {
+    verifyAndAssertMessages(
+      [
+        "type ResolveOptionType = {",
+          "depth?: number,",
+          "identifier?: string",
+        "};",
+        "",
+        "export default function resolve(",
+          "options: ResolveOptionType = {}",
+        "): Object {",
+          "options;",
+        "}",
+      ].join("\n"),
+      { "no-unused-vars": 1, "no-undef": 1 },
+      [ ]
+    )
+  });
 });