diff --git a/sub.py b/sub.py
index a0270c1..5708a89 100755
--- a/sub.py
+++ b/sub.py
@@ -39,7 +39,11 @@ def editSub(num):
     sub = getSub(getItem(num))
     if sub is None:
         sys.exit("This item does not have a sub")
-    editor = os.getenv("EDITOR").split()
+    editor = os.getenv("EDITOR")
+    if editor is not None and editor != "":
+        editor = editor.split()
+    else:
+        sys.exit("$EDITOR is unset, cannot edit")
     subprocess.call(editor + [os.path.join(os.getenv("TODO_DIR"), sub[0], sub[1])])
 
 def showSub(item, indent=0, color=True):