diff --git a/M2/include/M2/config.h.cmake b/M2/include/M2/config.h.cmake
index 9e40bb4dc33..fe6154d0bd2 100644
--- a/M2/include/M2/config.h.cmake
+++ b/M2/include/M2/config.h.cmake
@@ -333,6 +333,9 @@
 /* Whether we are building with tbb version >= 2021 */
 #cmakedefine WITH_TBB
 
+/* Whether we are building with an MPI library */
+#cmakedefine WITH_MPI
+
 /* whether we are linking with the libxml2 library */
 #cmakedefine WITH_XML