diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7e004fc..3b1d50a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,12 @@
 # cmake configuration
 
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
+    message(FATAL_ERROR
+            "In-tree builds are not supported; please perform an out-of-tree build:\n"
+            "    rm -rf CMakeCache.txt CMakeFiles/\n"
+            "    mkdir build && cd build && cmake ..")
+endif()
+
 cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
 cmake_policy(VERSION 3.1.0)
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}