diff --git a/Source/preinclude.h b/Source/preinclude.h
index 1a5e2c9..0ad206a 100644
--- a/Source/preinclude.h
+++ b/Source/preinclude.h
@@ -44,7 +44,7 @@
     #define CO2_UART_PORT 0x00
     #define HAL_UART_DMA 1
     #define HAL_UART_ISR 0
-    #define INT_HEAP_LEN 2256
+    #define INT_HEAP_LEN (2256 - 0xE)
 #elif defined(HAL_BOARD_CHDTECH_DEV)
     #define HAL_UART_DMA 1
     #define HAL_UART_ISR 2