diff --git a/src/Bloc/BlAlreadyAddedAsChildError.class.st b/src/Bloc/BlAlreadyAddedAsChildError.class.st
index f4c305367..1624ac9cb 100644
--- a/src/Bloc/BlAlreadyAddedAsChildError.class.st
+++ b/src/Bloc/BlAlreadyAddedAsChildError.class.st
@@ -8,7 +8,7 @@ Class {
 	#instVars : [
 		'element'
 	],
-	#category : 'Bloc-Basic-Errors'
+	#category : #'Bloc-Basic-Errors'
 }
 
 { #category : #'instance creation' }
@@ -18,7 +18,7 @@ BlAlreadyAddedAsChildError class >> element: anElement [
 
 { #category : #accessing }
 BlAlreadyAddedAsChildError >> description [
-	^ 'Can not add child that is already added to another element!'
+	^ ('Can not add {1} because it is already added to another element.') format: { self element }
 ]
 
 { #category : #accessing }
diff --git a/src/Bloc/BlElement.class.st b/src/Bloc/BlElement.class.st
index 33aca2f02..b489bdd7e 100644
--- a/src/Bloc/BlElement.class.st
+++ b/src/Bloc/BlElement.class.st
@@ -253,9 +253,10 @@ BlElement >> addChildren: aListOfElements [
 	self
 		assert: [ aListOfElements isNotNil ]
 		description: [ 'List of elements to add must not be nil' ].
-	self
-		assert: [ aListOfElements allSatisfy: [ :anElement | anElement parent isNil ] ]
-		description: [ 'All elements must not have parent' ].
+
+	aListOfElements do: [ :eachElement |
+		eachElement hasParent
+			ifTrue: [ (BlAlreadyAddedAsChildError element: eachElement) signal ] ].
 
 	"fast exit if there are no elements to add"
 	aListOfElements