diff --git a/src/PhpSpreadsheet/Helper/Migrator.php b/src/PhpSpreadsheet/Helper/Migrator.php
index 4eb60633..26d5fcea 100644
--- a/src/PhpSpreadsheet/Helper/Migrator.php
+++ b/src/PhpSpreadsheet/Helper/Migrator.php
@@ -4,6 +4,22 @@ namespace PhpOffice\PhpSpreadsheet\Helper;
 
 class Migrator
 {
+    /**
+     * @var string[]
+     */
+    private $from;
+
+    /**
+     * @var string[]
+     */
+    private $to;
+
+    public function __construct()
+    {
+        $this->from = array_keys($this->getMapping());
+        $this->to = array_values($this->getMapping());
+    }
+
     /**
      * Return the ordered mapping from old PHPExcel class names to new PhpSpreadsheet one.
      *
@@ -258,9 +274,6 @@ class Migrator
             '/*.phtml',
         ];
 
-        $from = array_keys($this->getMapping());
-        $to = array_values($this->getMapping());
-
         foreach ($patterns as $pattern) {
             foreach (glob($path . $pattern) as $file) {
                 if (strpos($path, '/vendor/') !== false) {
@@ -269,12 +282,7 @@ class Migrator
                     continue;
                 }
                 $original = file_get_contents($file);
-                $converted = str_replace($from, $to, $original);
-
-                // The string "PHPExcel" gets special treatment because of how common it might be.
-                // This regex requires a word boundary around the string, and it can't be
-                // preceded by $ or -> (goal is to filter out cases where a variable is named $PHPExcel or similar)
-                $converted = preg_replace('/(?<!\$|->)\bPHPExcel\b/', \PhpOffice\PhpSpreadsheet\Spreadsheet::class, $original);
+                $converted = $this->replace($original);
 
                 if ($original !== $converted) {
                     echo $file . " converted\n";
@@ -303,4 +311,23 @@ class Migrator
             $this->recursiveReplace($path);
         }
     }
+
+    /**
+     * Migrate the given code from PHPExcel to PhpSpreadsheet.
+     *
+     * @param string $original
+     *
+     * @return string
+     */
+    public function replace($original)
+    {
+        $converted = str_replace($this->from, $this->to, $original);
+
+        // The string "PHPExcel" gets special treatment because of how common it might be.
+        // This regex requires a word boundary around the string, and it can't be
+        // preceded by $ or -> (goal is to filter out cases where a variable is named $PHPExcel or similar)
+        $converted = preg_replace('~(?<!\$|->)(\b|\\\\)PHPExcel\b~', '\\' . \PhpOffice\PhpSpreadsheet\Spreadsheet::class, $converted);
+
+        return $converted;
+    }
 }
diff --git a/tests/PhpSpreadsheetTests/Helper/MigratorTest.php b/tests/PhpSpreadsheetTests/Helper/MigratorTest.php
index 3c9202c5..a64cda80 100644
--- a/tests/PhpSpreadsheetTests/Helper/MigratorTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/MigratorTest.php
@@ -17,4 +17,72 @@ class MigratorTest extends TestCase
             }
         }
     }
+
+    public function testReplace()
+    {
+        $input = <<<'STRING'
+<?php
+
+namespace Foo;
+
+use PHPExcel;
+use PHPExcel_Worksheet;
+
+class Bar
+{
+    /**
+     * @param PHPExcel $workbook
+     * @param PHPExcel_Worksheet $sheet
+     *
+     * @return string
+     */
+    public function baz(PHPExcel $workbook, PHPExcel_Worksheet $sheet)
+    {
+        PHPExcel::class;
+        \PHPExcel::class;
+        $PHPExcel->do();
+        $fooobjPHPExcel->do();
+        $objPHPExcel->do();
+        $this->objPHPExcel->do();
+        $this->PHPExcel->do();
+
+        return \PHPExcel_Cell::stringFromColumnIndex(9);
+    }
+}
+STRING;
+
+        $expected = <<<'STRING'
+<?php
+
+namespace Foo;
+
+use \PhpOffice\PhpSpreadsheet\Spreadsheet;
+use \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
+
+class Bar
+{
+    /**
+     * @param \PhpOffice\PhpSpreadsheet\Spreadsheet $workbook
+     * @param \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet $sheet
+     *
+     * @return string
+     */
+    public function baz(\PhpOffice\PhpSpreadsheet\Spreadsheet $workbook, \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet $sheet)
+    {
+        \PhpOffice\PhpSpreadsheet\Spreadsheet::class;
+        \PhpOffice\PhpSpreadsheet\Spreadsheet::class;
+        $PHPExcel->do();
+        $fooobjPHPExcel->do();
+        $objPHPExcel->do();
+        $this->objPHPExcel->do();
+        $this->PHPExcel->do();
+
+        return \PhpOffice\PhpSpreadsheet\Cell\Coordinate::stringFromColumnIndex(9);
+    }
+}
+STRING;
+
+        $migrator = new Migrator();
+        self::assertSame($expected, $migrator->replace($input));
+    }
 }