diff --git a/config/acme/machines/config_machines.xml b/config/acme/machines/config_machines.xml
index 5fcf03e8322..b907705018f 100644
--- a/config/acme/machines/config_machines.xml
+++ b/config/acme/machines/config_machines.xml
@@ -1028,6 +1028,9 @@
                <arg name="thread_count"> --envs OMP_NUM_THREADS=$OMP_NUM_THREADS</arg>
              </arguments>
          </mpirun>
+    <mpirun mpilib="mpi-serial">
+      <executable>unsupported</executable>
+    </mpirun>
     <module_system type="soft">
       <init_path lang="csh">/etc/profile.d/00softenv.csh</init_path>
       <cmd_path lang="csh">soft</cmd_path>
@@ -1121,6 +1124,9 @@
                <arg name="thread_count"> --envs OMP_NUM_THREADS=$OMP_NUM_THREADS</arg>
              </arguments>
          </mpirun>
+    <mpirun mpilib="mpi-serial">
+      <executable>unsupported</executable>
+    </mpirun>
     <module_system type="soft">
       <init_path lang="csh">/etc/profile.d/00softenv.csh</init_path>
       <cmd_path lang="csh">soft</cmd_path>
diff --git a/config/cesm/machines/config_machines.xml b/config/cesm/machines/config_machines.xml
index b6da2472d0e..43f8ded78b0 100644
--- a/config/cesm/machines/config_machines.xml
+++ b/config/cesm/machines/config_machines.xml
@@ -1163,6 +1163,9 @@
 	<arg name="thread_count"> --envs OMP_NUM_THREADS=$ENV{OMP_NUM_THREADS}</arg>
       </arguments>
     </mpirun>
+    <mpirun mpilib="mpi-serial">
+      <executable>unsupported</executable>
+    </mpirun>
     <module_system type="soft">
       <init_path lang="csh">/etc/profile.d/00softenv.csh</init_path>
       <init_path lang="sh">/etc/profile.d/00softenv.sh</init_path>
diff --git a/scripts/lib/CIME/XML/env_mach_specific.py b/scripts/lib/CIME/XML/env_mach_specific.py
index e49e2b81a80..a30cf28e07c 100644
--- a/scripts/lib/CIME/XML/env_mach_specific.py
+++ b/scripts/lib/CIME/XML/env_mach_specific.py
@@ -399,5 +399,7 @@ def get_mpirun(self, case, attribs, check_members=None, job="case.run", exe_only
         exec_node = self.get_node("executable", root=the_match)
         expect(exec_node is not None,"No executable found")
         executable = exec_node.text
-
+        expect("unsupported" not in executable, "%s is not supported for this machine"%attribs["mpilib"])
+        
+        
         return executable, args