diff --git a/TODO.md b/TODO.md
index 1ff3b26..deff0f1 100644
--- a/TODO.md
+++ b/TODO.md
@@ -17,3 +17,7 @@ Per @matthiasdebernardini, our current script no longer works.
 ## 3. Upgrade to 0.19.1
 
 We need to upgrade the whole tutorial to the newest BitCoin Core, and that means walking through it entirely, making sure it works, and redoing an examples with different output.
+
+## 4. Fix BTCBlock for Testnet
+
+The `btcblock` for testnet alias has had constant issues with the URLs delivering us total blockcounts for testnet going away. I'm not currently aware of any that work.