diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 5a07151b15..6a88cb308d 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -4816,7 +4816,7 @@ public function isInFirstLevelStatement(): bool
 
 	public function mergeWith(?self $otherScope): self
 	{
-		if ($otherScope === null) {
+		if ($otherScope === null || $this === $otherScope) {
 			return $this;
 		}
 		$ourExpressionTypes = $this->expressionTypes;