diff --git a/openmc/cmfd.py b/openmc/cmfd.py
index 91c264633..61bda9ed9 100644
--- a/openmc/cmfd.py
+++ b/openmc/cmfd.py
@@ -1090,6 +1090,12 @@ class CMFDRun:
         # Initialize parameters for CMFD tally windows
         self._set_tally_window()
 
+        # Extract spatial and energy indices
+        nx, ny, nz, ng = self._indices
+
+        # Initialize CMFD source to all ones
+        self._cmfd_src = np.ones((nx, ny, nz, ng))
+
         # Define all variables that will exist only on master process
         if openmc.lib.master():
             # Set global albedo
@@ -1101,9 +1107,6 @@ class CMFDRun:
             # Set up CMFD coremap
             self._set_coremap()
 
-            # Extract spatial and energy indices
-            nx, ny, nz, ng = self._indices
-
             # Allocate parameters that need to be stored for tally window
             self._openmc_src_rate = np.zeros((nx, ny, nz, ng, 0))
             self._flux_rate = np.zeros((nx, ny, nz, ng, 0))
diff --git a/openmc/lib/mesh.py b/openmc/lib/mesh.py
index 90db09397..79404c628 100644
--- a/openmc/lib/mesh.py
+++ b/openmc/lib/mesh.py
@@ -3,6 +3,7 @@ from ctypes import (c_int, c_int32, c_char_p, c_double, POINTER,
                     create_string_buffer)
 from weakref import WeakValueDictionary
 
+import numpy as np
 from numpy.ctypeslib import as_array
 
 from ..exceptions import AllocationError, InvalidIDError