diff --git a/packages/babel-core/test/fixtures/plugins/nested-if-alternate/exec.js b/packages/babel-core/test/fixtures/plugins/nested-if-alternate/exec.js
new file mode 100644
index 0000000000..c9dae86ffa
--- /dev/null
+++ b/packages/babel-core/test/fixtures/plugins/nested-if-alternate/exec.js
@@ -0,0 +1,19 @@
+var res = transform('', {
+  plugins: function (b) {
+    var t = b.types;
+    return {
+      visitor: {
+        Program: function(path) {
+          if (this.done) return;
+          // if (false) { if (true) 42; } else 23;
+          var inner = t.ifStatement(t.booleanLiteral(true), t.expressionStatement(t.numericLiteral(42)), null);
+          var outer = t.ifStatement(t.booleanLiteral(false), inner, t.expressionStatement(t.numericLiteral(23)));
+          path.replaceWith(t.program([outer]));
+          this.done = true;
+        }
+      }
+    }
+  }
+});
+
+assert.equal(eval(res.code), 23);
diff --git a/packages/babel-generator/src/generators/statements.js b/packages/babel-generator/src/generators/statements.js
index 744ff256d5..4e1e62393a 100644
--- a/packages/babel-generator/src/generators/statements.js
+++ b/packages/babel-generator/src/generators/statements.js
@@ -16,8 +16,21 @@ export function IfStatement(node: Object) {
   this.push(")");
   this.space();
 
+  let needsBlock = node.alternate && t.isIfStatement(node.consequent);
+  if (needsBlock) {
+    this.push("{");
+    this.newline();
+    this.indent();
+  }
+
   this.printAndIndentOnComments(node.consequent, node);
 
+  if (needsBlock) {
+    this.dedent();
+    this.newline();
+    this.push("}");
+  }
+
   if (node.alternate) {
     if (this.isLast("}")) this.space();
     this.push("else ");