diff --git a/vars.py b/vars.py
index e286bd3..ca048ff 100644
--- a/vars.py
+++ b/vars.py
@@ -4,6 +4,8 @@ TARGET = os.environ.get('REDO_TARGET', '')
 DEPTH = os.environ.get('REDO_DEPTH', '')
 DEBUG = os.environ.get('REDO_DEBUG', '') and 1 or 0
 VERBOSE = os.environ.get('REDO_VERBOSE', '') and 1 or 0
-BASE = os.path.abspath(os.environ['REDO_BASE'])
-while BASE.endswith('/'):
-    BASE = BASE[:-1]
+BASE = os.environ.get('REDO_BASE', '')
+if BASE:
+    BASE = os.path.abspath(BASE)
+    while BASE and BASE.endswith('/'):
+        BASE = BASE[:-1]