diff --git a/libs/core/async_mpi/CMakeLists.txt b/libs/core/async_mpi/CMakeLists.txt
index 1f403c003cb8..cca412736954 100644
--- a/libs/core/async_mpi/CMakeLists.txt
+++ b/libs/core/async_mpi/CMakeLists.txt
@@ -12,6 +12,8 @@ if(NOT ${HPX_WITH_ASYNC_MPI})
   return()
 endif()
 
+hpx_add_config_define(HPX_HAVE_ASYNC_MPI)
+
 # setup MPI, if necessary
 if(NOT TARGET Mpi::mpi)
   include(HPX_SetupMPI)