diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 68c2b04a34..a6c6d50d95 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -3907,6 +3907,8 @@ implementation
                   tObjectSymtable(symtable).datasize:=
                     tObjectSymtable(symtable).datasize+
                     tObjectSymtable(c.symtable).datasize;
+                  { inherit recordalignment }
+                  tObjectSymtable(symtable).recordalignment:=tObjectSymtable(c.symtable).recordalignment;
                   if (oo_has_vmt in objectoptions) and
                      (oo_has_vmt in c.objectoptions) then
                     tObjectSymtable(symtable).datasize:=
diff --git a/tests/webtbs/tw10454.pp b/tests/webtbs/tw10454.pp
new file mode 100644
index 0000000000..77bdbfdef4
--- /dev/null
+++ b/tests/webtbs/tw10454.pp
@@ -0,0 +1,22 @@
+{$mode objfpc}
+
+type
+  TMyObject = object
+    Int: longint;
+  end;
+
+  TMyObject2 = object(TMyObject)
+  end;
+
+  TMyClass = class
+    FByte: byte;
+    Obj: TMyObject2;  // instance of this object is not aligned
+  end;
+
+var
+  myclass: TMyClass;
+begin
+  myclass:=TMyClass.Create;
+  myclass.obj.int:=1; // Crash due to unaligned data access
+  myclass.Free;
+end.