diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5fee521ffbfd..e8cafabf4519 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -897,7 +897,7 @@ hpx_check_for_cxx11_noexcept(
   DEFINITIONS HPX_HAVE_CXX11_NOEXCEPT)
 
 hpx_check_for_cxx11_nullptr(
-  DEFINITIONS HPX_HAVE_CXX11_NULLPTR)
+  REQUIRED "HPX needs support for C++11 nullptr")
 
 hpx_check_for_cxx11_range_based_for(
   REQUIRED "HPX needs support for C++11 range-based for-loop")