diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2929f2b92a..0fdeac7740 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,13 @@
 cmake_minimum_required(VERSION 3.16)
 project(SerenityOS C CXX ASM)
 
+if(NOT "${CMAKE_BUILD_TYPE}" STREQUAL "")
+  message(FATAL
+    ": Don't use CMAKE_BUILD_TYPE when building serenity.\n"
+    "The default build type is optimized with debug info and asserts enabled,\n"
+    "and that's all there is.")
+endif()
+
 enable_testing()
 
 add_custom_target(image