diff --git a/src/Util/FileLoader.php b/src/Util/FileLoader.php
index 817ee70d699..73a02faba26 100644
--- a/src/Util/FileLoader.php
+++ b/src/Util/FileLoader.php
@@ -31,10 +31,19 @@ public static function checkAndLoad(string $filename): string
         $includePathFilename = \stream_resolve_include_path($filename);
         $localFile           = __DIR__ . \DIRECTORY_SEPARATOR . $filename;
 
-        /**
-         * @see https://github.com/sebastianbergmann/phpunit/pull/2751
+        /*
+         * Due to strict_types = 1 declaration, fopen() expects a string as the path parameter.
+         * If a boolean is provided as the path paramater, then a fatal TypeError is thrown, without
+         * describing what file has failed to load.
          */
-        $isReadable = @\fopen($includePathFilename, 'r') !== false;
+        if ($includePathFilename !== false) {
+            /**
+             * @see https://github.com/sebastianbergmann/phpunit/pull/2751
+             */
+            $isReadable = @\fopen($includePathFilename, 'r') !== false;
+        } else {
+            $isReadable = false;
+        }
 
         if (!$includePathFilename || !$isReadable || $includePathFilename === $localFile) {
             throw new Exception(