diff --git a/baselines/common/mpi_adam.py b/baselines/common/mpi_adam.py
index 17491d7..fd10bd5 100644
--- a/baselines/common/mpi_adam.py
+++ b/baselines/common/mpi_adam.py
@@ -1,7 +1,11 @@
-from mpi4py import MPI
 import baselines.common.tf_util as U
 import tensorflow as tf
 import numpy as np
+try:
+    from mpi4py import MPI
+except ImportError:
+    MPI = None
+    
 
 class MpiAdam(object):
     def __init__(self, var_list, *, beta1=0.9, beta2=0.999, epsilon=1e-08, scale_grad_by_procs=True, comm=None):
@@ -16,14 +20,15 @@ class MpiAdam(object):
         self.t = 0
         self.setfromflat = U.SetFromFlat(var_list)
         self.getflat = U.GetFlat(var_list)
-        self.comm = MPI.COMM_WORLD if comm is None else comm
+        self.comm = MPI.COMM_WORLD if comm is None and MPI is not None else comm
 
     def update(self, localg, stepsize):
         if self.t % 100 == 0:
             self.check_synced()
         localg = localg.astype('float32')
         globalg = np.zeros_like(localg)
-        self.comm.Allreduce(localg, globalg, op=MPI.SUM)
+        if self.comm is not None:
+            self.comm.Allreduce(localg, globalg, op=MPI.SUM)
         if self.scale_grad_by_procs:
             globalg /= self.comm.Get_size()
 
@@ -46,7 +51,8 @@ class MpiAdam(object):
         else:
             thetalocal = self.getflat()
             thetaroot = np.empty_like(thetalocal)
-            self.comm.Bcast(thetaroot, root=0)
+            if self.comm is not None:
+                self.comm.Bcast(thetaroot, root=0)
             assert (thetaroot == thetalocal).all(), (thetaroot, thetalocal)
 
 @U.in_session