diff --git a/mininet/node.py b/mininet/node.py
index 3c61393..371c0c0 100644
--- a/mininet/node.py
+++ b/mininet/node.py
@@ -383,23 +383,23 @@ class Node( object ):
                      'mncmd':
                      [ 'mnexec', '-da', str( self.pid ) ] }
         defaults.update( kwargs )
+        shell = defaults.pop( 'shell', False )
         if len( args ) == 1:
             if isinstance( args[ 0 ], list ):
                 # popen([cmd, arg1, arg2...])
                 cmd = args[ 0 ]
             elif isinstance( args[ 0 ], BaseString ):
                 # popen("cmd arg1 arg2...")
-                cmd = args[ 0 ].split()
+                cmd = [ args[ 0 ] ] if shell else args[ 0 ].split()
             else:
                 raise Exception( 'popen() requires a string or list' )
         elif len( args ) > 0:
             # popen( cmd, arg1, arg2... )
             cmd = list( args )
+        if shell:
+            cmd = [ os.environ[ 'SHELL' ], '-c' ] + [ ' '.join( cmd ) ]
         # Attach to our namespace  using mnexec -a
         cmd = defaults.pop( 'mncmd' ) + cmd
-        # Shell requires a string, not a list!
-        if defaults.get( 'shell', False ):
-            cmd = ' '.join( cmd )
         popen = self._popen( cmd, **defaults )
         return popen