diff --git a/CMakeLists.txt b/CMakeLists.txt
index a45ecdc..abb31a7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,8 +12,8 @@ set(CMAKE_SYSTEM_NAME Generic)
 set(CMAKE_C_COMPILER avr-gcc)
 set(OBJCOPY avr-objcopy)
 
-# Compiler flags
-set(CMAKE_C_FLAGS "-mmcu=${MCU} -DF_CPU=${F_CPU} -Os -Wall")
+# Compiler flags: optimize, warnings, treat warnings as errors
+set(CMAKE_C_FLAGS "-mmcu=${MCU} -DF_CPU=${F_CPU} -Os -Wall -Werror")
 
 # Sources
 add_executable(main.elf main.c)