diff --git a/lcl/include/customform.inc b/lcl/include/customform.inc
index b1e0cccd4a..df42fec83b 100644
--- a/lcl/include/customform.inc
+++ b/lcl/include/customform.inc
@@ -2422,7 +2422,7 @@ begin
                 Result := GetDefaultMonitor;
             poOwnerFormCenter:
               if (Owner is TCustomForm) and (GetParentForm(TCustomForm(Owner))<>Self) then
-                Result := Application.MainForm.Monitor
+                Result := TCustomForm(Owner).Monitor
               else
                 Result := GetDefaultMonitor;
           else