diff --git a/privacy/classes/local/request/moodle_content_writer.php b/privacy/classes/local/request/moodle_content_writer.php
index c212e271df8..2c642512bad 100644
--- a/privacy/classes/local/request/moodle_content_writer.php
+++ b/privacy/classes/local/request/moodle_content_writer.php
@@ -272,7 +272,9 @@ class moodle_content_writer implements content_writer {
         // Join the directory together with the name.
         $filepath = implode(DIRECTORY_SEPARATOR, $path) . DIRECTORY_SEPARATOR . $name;
 
-        return preg_replace('@' . DIRECTORY_SEPARATOR . '+@', DIRECTORY_SEPARATOR, $filepath);
+        // To use backslash, it must be doubled ("\\\\" PHP string).
+        $separator = str_replace('\\', '\\\\', DIRECTORY_SEPARATOR);
+        return preg_replace('@(' . $separator . '|/)+@', $separator, $filepath);
     }
 
     /**
@@ -291,7 +293,9 @@ class moodle_content_writer implements content_writer {
         // Join the directory together with the name.
         $filepath = implode(DIRECTORY_SEPARATOR, $path);
 
-        return preg_replace('@' . DIRECTORY_SEPARATOR . '+@', DIRECTORY_SEPARATOR, $filepath);
+        // To use backslash, it must be doubled ("\\\\" PHP string).
+        $separator = str_replace('\\', '\\\\', DIRECTORY_SEPARATOR);
+        return preg_replace('@(' . $separator . '|/)+@', $separator, $filepath);
     }
 
     /**
diff --git a/privacy/tests/moodle_content_writer_test.php b/privacy/tests/moodle_content_writer_test.php
index 7e20f64879b..66e6759b8f1 100644
--- a/privacy/tests/moodle_content_writer_test.php
+++ b/privacy/tests/moodle_content_writer_test.php
@@ -1162,12 +1162,18 @@ class moodle_content_writer_test extends advanced_testcase {
         if (null === $subcontext) {
             $rcm = $rc->getMethod('get_context_path');
             $rcm->setAccessible(true);
-            return $rcm->invoke($writer);
+            $path = $rcm->invoke($writer);
         } else {
             $rcm = $rc->getMethod('get_path');
             $rcm->setAccessible(true);
-            return $rcm->invoke($writer, $subcontext, $name);
+            $path = $rcm->invoke($writer, $subcontext, $name);
         }
+
+        // PHPUnit uses mikey179/vfsStream which is a stream wrapper for a virtual file system that uses '/'
+        // as the directory separator.
+        $path = str_replace(DIRECTORY_SEPARATOR, '/', $path);
+
+        return $path;
     }
 
     /**