diff --git a/src/Builder.php b/src/Builder.php
index 007323a..fa1f0cb 100644
--- a/src/Builder.php
+++ b/src/Builder.php
@@ -63,7 +63,7 @@ class Builder
     private function buildProperty($value, $key)
     {
         if (collect(['from', 'to'])->contains($key)) {
-            $value = collect($value)->implode('|');
+            $value = $this->implode($value);
         }
 
         return vsprintf("<apps:property name='%s' value='%s'/>", [
@@ -71,4 +71,12 @@ class Builder
             htmlentities($value),
         ]);
     }
+
+    /**
+     * Implode values with the appropriate prefix, suffix and separator.
+     */
+    private function implode($value, $separator = '|')
+    {
+        return sprintf('(%s)', collect($value)->implode($separator));
+    }
 }
diff --git a/tests/Unit/BuilderTest.php b/tests/Unit/BuilderTest.php
index a5f6029..a8c4b40 100644
--- a/tests/Unit/BuilderTest.php
+++ b/tests/Unit/BuilderTest.php
@@ -22,7 +22,7 @@ class BuilderTest extends TestCase
 
         $expected = <<<EOF
 <?xml version='1.0' encoding='UTF-8'?><feed xmlns='http://www.w3.org/2005/Atom' xmlns:apps='http://schemas.google.com/apps/2006'>
-<entry><apps:property name='from' value='foo@example.com|test@example.com'/><apps:property name='label' value='Some label'/><apps:property name='shouldArchive' value='true'/></entry>
+<entry><apps:property name='from' value='(foo@example.com|test@example.com)'/><apps:property name='label' value='Some label'/><apps:property name='shouldArchive' value='true'/></entry>
 <entry><apps:property name='hasTheWord' value='from:bar@example.com'/><apps:property name='shouldStar' value='true'/><apps:property name='shouldAlwaysMarkAsImportant' value='true'/></entry>
 </feed>
 EOF;