diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index 6d4727348f..9f0ea6ec5c 100644
--- a/pkg_resources/__init__.py
+++ b/pkg_resources/__init__.py
@@ -2981,6 +2981,7 @@ def _initialize_master_working_set():
     # ensure that all distributions added to the working set in the future
     # (e.g. by calling ``require()``) will get activated as well,
     # with higher priority (replace=True).
+    dist = None # ensure dist is defined for del dist below
     for dist in working_set:
         dist.activate(replace=False)
     del dist