diff --git a/pkgs/development/python-modules/h5py/default.nix b/pkgs/development/python-modules/h5py/default.nix
index e9bae3f8206..bdbdcdcc2e7 100644
--- a/pkgs/development/python-modules/h5py/default.nix
+++ b/pkgs/development/python-modules/h5py/default.nix
@@ -1,6 +1,6 @@
 { stdenv, fetchurl, python, buildPythonPackage
 , numpy, hdf5, cython, six, pkgconfig
-, mpi4py ? null }:
+, mpi4py ? null, openssh }:
 
 assert hdf5.mpiSupport -> mpi4py != null && hdf5.mpi == mpi4py.mpi;
 
@@ -24,6 +24,10 @@ in buildPythonPackage rec {
 
   postConfigure = ''
     ${python.executable} setup.py configure ${configure_flags}
+
+    # Needed to run the tests reliably. See:
+    # https://bitbucket.org/mpi4py/mpi4py/issues/87/multiple-test-errors-with-openmpi-30
+    ${optionalString mpiSupport "export OMPI_MCA_rmaps_base_oversubscribe=yes"}
   '';
 
   preBuild = if mpiSupport then "export CC=${mpi}/bin/mpicc" else "";
@@ -33,7 +37,7 @@ in buildPythonPackage rec {
     ++ optional mpiSupport mpi
     ;
   propagatedBuildInputs = [ numpy six]
-    ++ optional mpiSupport mpi4py
+    ++ optionals mpiSupport [ mpi4py openssh ]
     ;
 
   meta = {
diff --git a/pkgs/development/python-modules/mpi4py/default.nix b/pkgs/development/python-modules/mpi4py/default.nix
index fcbca62ff9d..9329d386099 100644
--- a/pkgs/development/python-modules/mpi4py/default.nix
+++ b/pkgs/development/python-modules/mpi4py/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, fetchPypi, python, buildPythonPackage, mpi }:
+{ stdenv, fetchPypi, python, buildPythonPackage, mpi, openssh }:
 
 buildPythonPackage rec {
   pname = "mpi4py";
@@ -28,11 +28,15 @@ buildPythonPackage rec {
     # sometimes packages specify where files should be installed outside the usual
     # python lib prefix, we override that back so all infrastructure (setup hooks)
     # work as expected
+
+    # Needed to run the tests reliably. See:
+    # https://bitbucket.org/mpi4py/mpi4py/issues/87/multiple-test-errors-with-openmpi-30
+    export OMPI_MCA_rmaps_base_oversubscribe=yes
   '';
 
   setupPyBuildFlags = ["--mpicc=${mpi}/bin/mpicc"];
 
-  buildInputs = [ mpi ];
+  buildInputs = [ mpi openssh ];
 
   meta = {
     description =