diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,21 +37,6 @@ message(STATUS "default momentum and length are ${HEPMC_DEFAULT_MOM_UNIT} ${HEPM
 # find the HepMC cmake modules
 set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules ${CMAKE_MODULE_PATH})
 
-# make sure we are not building from within the source code directory
-string(COMPARE EQUAL "${CMAKE_SOURCE_DIR}" "${CMAKE_BINARY_DIR}" in_source)
-string( REGEX MATCH "${CMAKE_SOURCE_DIR}/" in_source_subdir
-"${CMAKE_BINARY_DIR}")
-if (in_source OR in_source_subdir)
-  message(FATAL_ERROR "
-ERROR: In source builds of this project are not allowed.
-A separate build directory is required.
-Please create one and run cmake from the build directory.
-Also note that cmake has just added files to your source code directory.
-We suggest getting a new copy of the source code.
-Otherwise, delete `CMakeCache.txt' and the directory `CMakeFiles'.
-  ")
-endif ()
-
 # build_docs is OFF (false) by default
 if ( build_docs )
    message(STATUS "documents WILL be built and installed" )