diff --git a/mininet/cli.py b/mininet/cli.py
index 3ca190f722d487436464aac231f0519ac5634251..67823de6a2c1de6d3ec9c3bb49e256f80948c616 100644
--- a/mininet/cli.py
+++ b/mininet/cli.py
@@ -297,6 +297,7 @@ def do_source( self, line ):
                     break
         except IOError:
             error( 'error reading file %s\n' % args[ 0 ] )
+        self.inputFile.close()
         self.inputFile = None
 
     def do_dpctl( self, line ):