diff --git a/packages/babel-plugin-transform-es2015-parameters/src/params.js b/packages/babel-plugin-transform-es2015-parameters/src/params.js
index 73215cbd09..e5e4dc0105 100644
--- a/packages/babel-plugin-transform-es2015-parameters/src/params.js
+++ b/packages/babel-plugin-transform-es2015-parameters/src/params.js
@@ -54,53 +54,41 @@ export default function convertFunctionParams(path, loose) {
   };
 
   const body = [];
-
-  let firstOptionalIndex = null;
-
-  //
   const params = path.get("params");
 
-  if (loose) {
-    const body = [];
-    for (let i = 0; i < params.length; ++i) {
-      const param = params[i];
-      if (param.isAssignmentPattern()) {
-        const left = param.get("left");
-        const right = param.get("right");
-
-        const undefinedNode = scope.buildUndefinedNode();
-
-        if (left.isIdentifier()) {
-          body.push(
-            buildLooseDefaultParam({
-              ASSIGNMENT_IDENTIFIER: left.node,
-              DEFAULT_VALUE: right.node,
-              UNDEFINED: undefinedNode,
-            }),
-          );
-          param.replaceWith(left.node);
-        } else if (left.isObjectPattern() || left.isArrayPattern()) {
-          const paramName = scope.generateUidIdentifier();
-          body.push(
-            buildLooseDestructuredDefaultParam({
-              ASSIGNMENT_IDENTIFIER: left.node,
-              DEFAULT_VALUE: right.node,
-              PARAMETER_NAME: paramName,
-              UNDEFINED: undefinedNode,
-            }),
-          );
-          param.replaceWith(paramName);
-        }
-      }
-    }
-    path.get("body").unshiftContainer("body", body);
-    return;
-  }
+  let firstOptionalIndex = null;
 
   for (let i = 0; i < params.length; i++) {
     const param = params[i];
 
-    if (param.isAssignmentPattern()) {
+    if (param.isAssignmentPattern() && loose) {
+      const left = param.get("left");
+      const right = param.get("right");
+
+      const undefinedNode = scope.buildUndefinedNode();
+
+      if (left.isIdentifier()) {
+        body.push(
+          buildLooseDefaultParam({
+            ASSIGNMENT_IDENTIFIER: left.node,
+            DEFAULT_VALUE: right.node,
+            UNDEFINED: undefinedNode,
+          }),
+        );
+        param.replaceWith(left.node);
+      } else if (left.isObjectPattern() || left.isArrayPattern()) {
+        const paramName = scope.generateUidIdentifier();
+        body.push(
+          buildLooseDestructuredDefaultParam({
+            ASSIGNMENT_IDENTIFIER: left.node,
+            DEFAULT_VALUE: right.node,
+            PARAMETER_NAME: paramName,
+            UNDEFINED: undefinedNode,
+          }),
+        );
+        param.replaceWith(paramName);
+      }
+    } else if (param.isAssignmentPattern()) {
       if (firstOptionalIndex === null) firstOptionalIndex = i;
 
       const left = param.get("left");
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/default-rest-mix/actual.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/default-rest-mix/actual.js
new file mode 100644
index 0000000000..ea2ac402c2
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/default-rest-mix/actual.js
@@ -0,0 +1,8 @@
+function fn(
+  a1,
+  a2 = 4,
+  {a3, a4},
+  a5,
+  {a6, a7} = {}) {
+
+}
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/default-rest-mix/expected.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/default-rest-mix/expected.js
new file mode 100644
index 0000000000..5db7bb23c0
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/default-rest-mix/expected.js
@@ -0,0 +1,12 @@
+function fn(a1, a2, _ref, a5, _temp) {
+  if (a2 === void 0) {
+    a2 = 4;
+  }
+
+  var a3 = _ref.a3,
+      a4 = _ref.a4;
+
+  var _ref2 = _temp === void 0 ? {} : _temp,
+      a6 = _ref2.a6,
+      a7 = _ref2.a7;
+}
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/destructuring-rest/actual.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/destructuring-rest/actual.js
new file mode 100644
index 0000000000..3b538fe704
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/destructuring-rest/actual.js
@@ -0,0 +1,4 @@
+// #3861
+function t(x = "default", { a, b }, ...args) {
+  console.log(x, a, b, args);
+}
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/destructuring-rest/expected.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/destructuring-rest/expected.js
new file mode 100644
index 0000000000..ba4ffd854e
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/use-loose-option/destructuring-rest/expected.js
@@ -0,0 +1,15 @@
+// #3861
+function t(x, _ref) {
+  if (x === void 0) {
+    x = "default";
+  }
+
+  var a = _ref.a,
+      b = _ref.b;
+
+  for (var _len = arguments.length, args = new Array(_len > 2 ? _len - 2 : 0), _key = 2; _key < _len; _key++) {
+    args[_key - 2] = arguments[_key];
+  }
+
+  console.log(x, a, b, args);
+}