diff --git a/CHANGELOG.md b/CHANGELOG.md
index fde44bc2f3..6899c4734a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@ Updates should follow the [Keep a CHANGELOG](https://keepachangelog.com/) princi
 
 ## [Unreleased][unreleased]
 
+### Changed
+
+ - Blocks added outside of the parsing context now have their start/end line numbers defaulted to 0 to avoid type errors (#579)
+
 ### Fixed
 
  - Fixed replacement blocks not inheriting the start line number of the container they're replacing (#579)
diff --git a/src/Block/Element/AbstractBlock.php b/src/Block/Element/AbstractBlock.php
index b8ac83b527..1edd683f2a 100644
--- a/src/Block/Element/AbstractBlock.php
+++ b/src/Block/Element/AbstractBlock.php
@@ -45,12 +45,12 @@ abstract class AbstractBlock extends Node
     /**
      * @var int
      */
-    protected $startLine;
+    protected $startLine = 0;
 
     /**
      * @var int
      */
-    protected $endLine;
+    protected $endLine = 0;
 
     protected function setParent(Node $node = null)
     {