diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2a7b3efe1e5..f4988b856cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -200,7 +200,8 @@ elseif(CONFIG_SPEED_OPTIMIZATIONS)
 elseif(CONFIG_SIZE_OPTIMIZATIONS)
   set(OPTIMIZATION_FLAG ${OPTIMIZE_FOR_SIZE_FLAG}) # Default in kconfig
 else()
-  assert(0 "Unreachable code. Expected optimization level to have been chosen. See Kconfig.zephyr")
+  message(FATAL_ERROR
+    "Unreachable code. Expected optimization level to have been chosen. See Kconfig.zephyr")
 endif()
 
 if(NOT CONFIG_ARCH_IS_SET)
@@ -247,7 +248,8 @@ if(CONFIG_CPP)
     set(STD_CPP_DIALECT_FLAGS $<TARGET_PROPERTY:compiler-cpp,dialect_cpp2b>)
     list(APPEND CMAKE_CXX_COMPILE_FEATURES ${compile_features_cpp20})
   else()
-    assert(0 "Unreachable code. Expected C++ standard to have been chosen. See Kconfig.zephyr.")
+    message(FATAL_ERROR
+      "Unreachable code. Expected C++ standard to have been chosen. See Kconfig.zephyr.")
   endif()
   set(CMAKE_CXX_COMPILE_FEATURES ${CMAKE_CXX_COMPILE_FEATURES} PARENT_SCOPE)