diff --git a/homeassistant/components/system_log/__init__.py b/homeassistant/components/system_log/__init__.py
index 16786bdeba4845..d6877c32f0deee 100644
--- a/homeassistant/components/system_log/__init__.py
+++ b/homeassistant/components/system_log/__init__.py
@@ -91,15 +91,15 @@ def __init__(self, record, stack, source):
         self.first_occured = self.timestamp = record.created
         self.level = record.levelname
         self.message = record.getMessage()
+        self.exception = ''
+        self.root_cause = None
         if record.exc_info:
             self.exception = ''.join(
                 traceback.format_exception(*record.exc_info))
             _, _, tb = record.exc_info  # pylint: disable=invalid-name
             # Last line of traceback contains the root cause of the exception
-            self.root_cause = str(traceback.extract_tb(tb)[-1])
-        else:
-            self.exception = ''
-            self.root_cause = None
+            if traceback.extract_tb(tb):
+                self.root_cause = str(traceback.extract_tb(tb)[-1])
         self.source = source
         self.count = 1