diff --git a/readthedocs/projects/tasks.py b/readthedocs/projects/tasks.py
index 39145b3189c..80be5d8342f 100644
--- a/readthedocs/projects/tasks.py
+++ b/readthedocs/projects/tasks.py
@@ -390,8 +390,11 @@ def run(
                     'stack': True,
                     'tags': {
                         'build': build_pk,
-                        'project': self.project.slug,
-                        'version': self.version.slug,
+                        # We can't depend on these objects because the api
+                        # could fail. But self.project and self.version are
+                        # initialized as empty dicts in the init method.
+                        'project': self.project.slug if self.project else None,
+                        'version': self.version.slug if self.version else None,
                     },
                 },
             )