diff --git a/contrib/opencensus-ext-azure/opencensus/ext/azure/trace_exporter/__init__.py b/contrib/opencensus-ext-azure/opencensus/ext/azure/trace_exporter/__init__.py
index 8a54bc2cb..fbec78c98 100644
--- a/contrib/opencensus-ext-azure/opencensus/ext/azure/trace_exporter/__init__.py
+++ b/contrib/opencensus-ext-azure/opencensus/ext/azure/trace_exporter/__init__.py
@@ -101,7 +101,7 @@ def span_data_to_envelope(self, sd):
                 data = ExceptionData(
                     exceptions=[{
                         'id': 1,
-                        'outerId': '{}'.format(sd.span_id),
+                        'outerId': sd.span_id,
                         'typeName': sd.attributes.get(ERROR_NAME, ''),
                         'message': sd.attributes[ERROR_MESSAGE],
                         'hasFullStack': STACKTRACE in sd.attributes,