diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7849e2a..2ca52a2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -182,7 +182,10 @@ target_compile_options(firmware PRIVATE -Wdouble-promotion)
 
 # target_link_libraries( firmware PRIVATE A3idesHeaders )
 
-target_sources(firmware PRIVATE src/main.cpp)
+target_sources(firmware PRIVATE
+  src/main.cpp
+  src/hal/avr/cpu.cpp
+)
 
 set_property(
   SOURCE src/version.c