diff --git a/sources/Forms/FormBuilder/DependencyMap.php b/sources/Forms/FormBuilder/DependencyMap.php
index 88c05deac..61a3fe279 100644
--- a/sources/Forms/FormBuilder/DependencyMap.php
+++ b/sources/Forms/FormBuilder/DependencyMap.php
@@ -124,10 +124,12 @@ class DependencyMap
 	public function GetImpacted(string $sBlockName): array
 	{
 		$aImpacted = [];
-		foreach ($this->aOutputToInputsMap[$sBlockName] as $aBindings) {
-			foreach ($aBindings as $oBinding) {
-				$oDestBlock = $oBinding->oDestinationIO->GetOwnerBlock();
-				$aImpacted[] = $oDestBlock;
+		if (array_key_exists($sBlockName, $this->aOutputToInputsMap)) {
+			foreach ($this->aOutputToInputsMap[$sBlockName] as $aBindings) {
+				foreach ($aBindings as $oBinding) {
+					$oDestBlock = $oBinding->oDestinationIO->GetOwnerBlock();
+					$aImpacted[] = $oDestBlock;
+				}
 			}
 		}