diff --git a/README.rst b/README.rst
index 9825f3c3b2e6ad1f3afc65ce2ff0c3f358f417a2..0997e9bc97ff11be477955163c44f5099358c543 100644
--- a/README.rst
+++ b/README.rst
@@ -115,6 +115,9 @@ The list is a work in progress, please contact us
 (Cristian.Lalescu@ds.mpg.de) if the procedure fails at any step of the
 process.
 
+*Note*: the HDF5 library may require MPI standard v1, we haven't tested
+this in detail. Some default OpenMPI3 installations will not work.
+
 Detailed full installation instructions:
 
 1.