diff --git a/phpBB/phpbb/storage/adapter/adapter_interface.php b/phpBB/phpbb/storage/adapter/adapter_interface.php
index a52585a42f..fa824703b7 100644
--- a/phpBB/phpbb/storage/adapter/adapter_interface.php
+++ b/phpBB/phpbb/storage/adapter/adapter_interface.php
@@ -99,7 +99,9 @@ interface adapter_interface
 	/*
 	 * Get space available in bytes.
 	 *
-	 * @return mixed	Returns available space or false when unable to retrieve available space
+	 * @throws \phpbb\storage\exception\exception		When unable to retrieve available storage space
+	 *
+	 * @return float	Returns available space
 	 */
 	public function free_space();
 }
diff --git a/phpBB/phpbb/storage/adapter/local.php b/phpBB/phpbb/storage/adapter/local.php
index 3cde5a4fbb..fbbb92fb17 100644
--- a/phpBB/phpbb/storage/adapter/local.php
+++ b/phpBB/phpbb/storage/adapter/local.php
@@ -432,6 +432,11 @@ class local implements adapter_interface, stream_interface
 	{
 		$free_space = @disk_free_space($this->root_path);
 
+		if ($free_space === false)
+		{
+			throw new exception('STORAGE_CANNOT_GET_FREE_SPACE');
+		}
+
 		return $free_space;
 	}
 }
diff --git a/phpBB/phpbb/storage/storage.php b/phpBB/phpbb/storage/storage.php
index ad5d0ed240..7e84e49e62 100644
--- a/phpBB/phpbb/storage/storage.php
+++ b/phpBB/phpbb/storage/storage.php
@@ -390,13 +390,12 @@ class storage
 	/**
 	 * Get space available in bytes.
 	 *
-	 * @throws \phpbb\storage\exception\exception		When can't get available space
+	 * @throws \phpbb\storage\exception\exception		When unable to retrieve available storage space
 	 *
-	 * @return mixed	Returns available space or false when unable to retrieve available space
+	 * @return float	Returns available space
 	 */
 	public function free_space()
 	{
 		return $this->get_adapter()->free_space();
 	}
-
 }