diff --git a/gcc/ada/sem_aggr.adb b/gcc/ada/sem_aggr.adb
index 051a650f9c26..21d620716f04 100644
--- a/gcc/ada/sem_aggr.adb
+++ b/gcc/ada/sem_aggr.adb
@@ -2113,7 +2113,7 @@ package body Sem_Aggr is
 
       function Valid_Ancestor_Type return Boolean;
       --  Verify that the type of the ancestor part is a non-private ancestor
-      --  of the expected type.
+      --  of the expected type, which must be a type extension.
 
       ----------------------------
       -- Valid_Limited_Ancestor --
@@ -2159,8 +2159,8 @@ package body Sem_Aggr is
             Imm_Type := Etype (Base_Type (Imm_Type));
          end loop;
 
-         if Etype (Imm_Type) /= Base_Type (A_Type)
-           or else Base_Type (Typ) = Base_Type (A_Type)
+         if not Is_Derived_Type (Base_Type (Typ))
+           or else Etype (Imm_Type) /= Base_Type (A_Type)
          then
             Error_Msg_NE ("expect ancestor type of &", A, Typ);
             return False;