diff --git a/ssm/message_directory.py b/ssm/message_directory.py
index b7a70c65..62dad40d 100644
--- a/ssm/message_directory.py
+++ b/ssm/message_directory.py
@@ -87,8 +87,9 @@ def _get_messages(self, sort_by_mtime=False):
         """
         try:
             # Get a list of files under self.directory_path
-            # in an arbitrary order.
-            file_name_list = os.listdir(self.directory_path)
+            # in an arbitrary order (ignoring directories).
+            file_name_list = [file for file in os.listdir(self.directory_path)
+                              if os.path.isfile(os.path.join(self.directory_path, file))]
 
             if sort_by_mtime:
                 # Working space to hold the unsorted messages
diff --git a/test/test_message_directory.py b/test/test_message_directory.py
index af78bdc7..2e3d8541 100644
--- a/test/test_message_directory.py
+++ b/test/test_message_directory.py
@@ -14,6 +14,7 @@
 """This module contains test cases for the MessageDirectory class."""
 from __future__ import print_function
 
+import os
 import shutil
 import tempfile
 import time
@@ -27,7 +28,7 @@ class TestMessageDirectory(unittest.TestCase):
 
     def setUp(self):
         """Create a MessageDirectory class on top of a temporary directory."""
-        self.tmp_dir = tempfile.mkdtemp(prefix='message_directory')
+        self.tmp_dir = tempfile.mkdtemp(prefix='message_directory_')
         self.message_directory = MessageDirectory(self.tmp_dir)
 
     def test_add_and_get(self):
@@ -137,6 +138,19 @@ def test_remove(self):
         # Check the count method returns the expected value.
         self.assertEqual(self.message_directory.count(), 0)
 
+    def test_dir_in_dir(self):
+        """Check that directories inside the queue are being ignored."""
+        self.longMessage = True  # Include normal unittest output before custom message.
+
+        # Add a single test file (closing it to ensure this works on Unix)
+        handle, _path = tempfile.mkstemp(dir=self.tmp_dir)
+        os.close(handle)
+        # Add a directory (to ignore)
+        tempfile.mkdtemp(prefix='extra_directory_', dir=self.tmp_dir)
+
+        self.assertEqual(self.message_directory.count(), 1, "Expected just one file, "
+                         "but greater result implies that directory is being counted.")
+
     def tearDown(self):
         """Remove test directory and all contents."""
         try: