diff --git a/CMakeLists.txt b/CMakeLists.txt
index 04f39a3..90815bb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,12 @@
+# Set minimum required version for CMake
 cmake_minimum_required(VERSION 3.10)
 
+# Prevent in-source builds
+if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
+  message(FATAL_ERROR "In-source builds are not allowed. Please create a separate\
+   build directory and run CMake from there.")
+endif()
+
 # workaround for https://gitlab.kitware.com/cmake/cmake/issues/16967
 if(${CMAKE_VERSION} VERSION_LESS "3.12.0")
     project(rx888)