However, I didn't mention How the Dragon Was Tricked. In which the hero (disguised as a beggar) argues with the dragon about whether a box is big enough to hold the hero. The hero tells the dragon that he and the dragon are the same size, so if it hold him, it will hold the hero. And the dragon falls for it; he tests the box and the hero traps him.
Dragons in Eastern Europe lore are smaller than those further west.