diff --git a/poetry/utils/env.py b/poetry/utils/env.py
index 0a027bd668a..ccd855b5c60 100644
--- a/poetry/utils/env.py
+++ b/poetry/utils/env.py
@@ -1212,7 +1212,7 @@ def unset_env(self, key):
             del os.environ[key]
 
     def _updated_path(self):
-        return os.pathsep.join([str(self._bin_dir), os.environ["PATH"]])
+        return os.pathsep.join([str(self._bin_dir), os.environ.get("PATH", "")])
 
 
 class NullEnv(SystemEnv):