diff --git a/CMakeLists.txt b/CMakeLists.txt
index a340289a84..3223182746 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,6 +6,13 @@
 #
 # ----------------------------------------------------------------------------
 
+# Disable in-source builds to prevent source tree corruption.
+if(" ${CMAKE_SOURCE_DIR}" STREQUAL " ${CMAKE_BINARY_DIR}")
+  message(FATAL_ERROR "
+FATAL: In-source builds are not allowed.
+       You should create separate directory for build files.
+")
+endif()
 
 
 include(cmake/OpenCVMinDepVersions.cmake)
@@ -1397,13 +1404,6 @@ status("")
 
 ocv_finalize_status()
 
-# ----------------------------------------------------------------------------
-# Warn in the case of in-source build
-# ----------------------------------------------------------------------------
-if("${CMAKE_CURRENT_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_BINARY_DIR}")
-  message(WARNING "The source directory is the same as binary directory. \"make clean\" may damage the source tree")
-endif()
-
 # ----------------------------------------------------------------------------
 # CPack stuff
 # ----------------------------------------------------------------------------