diff --git a/bilby/core/sampler/dynesty.py b/bilby/core/sampler/dynesty.py
index cedc5aca6e441d21fe781ca3a470799d3cb8e3f4..23c6a7604b67b1835f376c52356bcbb1356e0903 100644
--- a/bilby/core/sampler/dynesty.py
+++ b/bilby/core/sampler/dynesty.py
@@ -436,8 +436,9 @@ class Dynesty(NestedSampler):
         logger.info("Writing checkpoint file {}".format(self.resume_file))
 
         end_time = datetime.datetime.now()
-        self.sampling_time += end_time - self.start_time
-        self.start_time = end_time
+        if hasattr(self, 'start_time'):
+            self.sampling_time += end_time - self.start_time
+            self.start_time = end_time
 
         current_state = dict(
             unit_cube_samples=self.sampler.saved_u,