diff --git a/pypandoc/__init__.py b/pypandoc/__init__.py
index 232caaa..aa6a607 100644
--- a/pypandoc/__init__.py
+++ b/pypandoc/__init__.py
@@ -414,6 +414,10 @@ def _classify_pandoc_logging(raw, default_level="WARNING"):
     
     log_msgs = [first.replace('[{}] '.format(level), '')]
     
+    if level not in level_map:
+        level = default_level
+    
+    
     for msg in msgs:
         
         search = re.search(r"\[(.*?)\]", msg)
diff --git a/tests.py b/tests.py
index b1dcef1..6454159 100755
--- a/tests.py
+++ b/tests.py
@@ -334,6 +334,19 @@ def test_classify_pandoc_logging_default(self):
             self.assertEqual(expected_msgs[i], m)
 
 
+    def test_classify_pandoc_logging_invalid_level(self):
+        
+        test = ("[WARN] This is some message on\ntwo lines\n"
+                "[ERROR] This is a second message.")
+        expected_levels = [30, 40]
+        expected_msgs = ["This is some message on\ntwo lines",
+                         "This is a second message."]
+        
+        for i, (l, m) in enumerate(pypandoc._classify_pandoc_logging(test)):
+            self.assertEqual(expected_levels[i], l)
+            self.assertEqual(expected_msgs[i], m)
+
+
     def test_conversion_stderr(self):
         
         # Clear logger handlers