diff --git a/pureboot/pureboot.cpp b/pureboot/pureboot.cpp
index 7881008..9dd36db 100644
--- a/pureboot/pureboot.cpp
+++ b/pureboot/pureboot.cpp
@@ -488,8 +488,7 @@ void fill_page(std::uint8_t bank, std::uint16_t at)
 	// address is a word address and a slot is half as many words as bytes, so
 	// its high byte is the slot index outright. No absolute address is ever
 	// formed, so the image stays position-independent.
-	const auto return_words = reinterpret_cast<std::uint16_t>(__builtin_return_address(0));
-	const auto slot_high = static_cast<std::uint8_t>(return_words >> 8);
+	const auto slot_high = avr::startup::caller_page();
 
 	await_host();