diff --git a/src/SpriteLang-Tests/L8PosTest.class.st b/src/SpriteLang-Tests/L8PosTest.class.st
index 4064dcc0f..91b6a1b75 100644
--- a/src/SpriteLang-Tests/L8PosTest.class.st
+++ b/src/SpriteLang-Tests/L8PosTest.class.st
@@ -6,7 +6,7 @@ Class {
 
 { #category : #tests }
 L8PosTest >> test_append [
-	self skip
+	self skip "cf. #tcInvs"
 ]
 
 { #category : #tests }
diff --git a/src/SpriteLang/Array.extension.st b/src/SpriteLang/Array.extension.st
index b2fee774d..575a06789 100644
--- a/src/SpriteLang/Array.extension.st
+++ b/src/SpriteLang/Array.extension.st
@@ -26,5 +26,5 @@ tcInvs :: [SrcData] -> F.SEnv Reft
 				| inv |
 				inv := d inv.
 				inv isKnown and: [ inv expr pTrivial not ]
-			]) collect: [ :d | d shouldBeImplemented ])
+			]) collect: [ :d | d shouldBeImplemented "L8 test_append" ])
 ]