diff --git a/CHANGELOG.md b/CHANGELOG.md
index ce6da94e..803f974a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -66,6 +66,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Exclude the vendor folder in migration - [#481](https://github.com/PHPOffice/PhpSpreadsheet/issues/481)
 - Chained operations on cell ranges involving borders operated on last cell only [#428](https://github.com/PHPOffice/PhpSpreadsheet/issues/428)
 - Avoid memory exhaustion when cloning worksheet with a drawing [#437](https://github.com/PHPOffice/PhpSpreadsheet/issues/437)
+- Migration tool keep variables containing $PHPExcel untouched [#598](https://github.com/PHPOffice/PhpSpreadsheet/issues/598)
 
 ## [1.3.1] - 2018-06-12
 
diff --git a/src/PhpSpreadsheet/Helper/Migrator.php b/src/PhpSpreadsheet/Helper/Migrator.php
index 93686626..4eb60633 100644
--- a/src/PhpSpreadsheet/Helper/Migrator.php
+++ b/src/PhpSpreadsheet/Helper/Migrator.php
@@ -204,7 +204,6 @@ class Migrator
             'PHPExcel_Settings' => \PhpOffice\PhpSpreadsheet\Settings::class,
             'PHPExcel_Style' => \PhpOffice\PhpSpreadsheet\Style\Style::class,
             'PHPExcel_Worksheet' => \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet::class,
-            'PHPExcel' => \PhpOffice\PhpSpreadsheet\Spreadsheet::class,
         ];
 
         $methods = [
@@ -272,6 +271,11 @@ class Migrator
                 $original = file_get_contents($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, $original);
+
                 if ($original !== $converted) {
                     echo $file . " converted\n";
                     file_put_contents($file, $converted);