diff --git a/CMakeLists.txt b/CMakeLists.txt
index e2329c69..cbc091c6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,6 +8,10 @@ endif()
 
 project(Catch2 LANGUAGES CXX VERSION 2.7.2)
 
+if (CMAKE_BINARY_DIR STREQUAL CMAKE_SOURCE_DIR)
+    message(FATAL_ERROR "Building in-source is not supported! Create a build dir and remove ${CMAKE_SOURCE_DIR}/CMakeCache.txt")
+endif()
+
 # Provide path for scripts
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/CMake")