diff --git a/src/rp2040_arduino_platform.cpp b/src/rp2040_arduino_platform.cpp
index ca64b16..e901502 100644
--- a/src/rp2040_arduino_platform.cpp
+++ b/src/rp2040_arduino_platform.cpp
@@ -39,7 +39,7 @@ A RAM-buffered Flash can be use by defining USE_RP2040_LARGE_EEPROM_EMULATION
 #error "KNX_FLASH_SIZE must be multiple of 4096"
 #endif
 
-#if KNX_FLASH_SIZE%4096
+#if KNX_FLASH_OFFSET%4096
 #error "KNX_FLASH_OFFSET must be multiple of 4096"
 #endif