diff --git a/README.md b/README.md
index 0d59f1d..add9593 100644
--- a/README.md
+++ b/README.md
@@ -29,7 +29,7 @@ pip install cashu
 
 To update Cashu, use `pip install cashu -U`. 
 
-If you have problems running the command above on Ubuntu, run `sudo apt install -y pip pkg-config libpq-dev`. On macOS, run `brew install postgresql`.
+If you have problems running the command above on Ubuntu, run `sudo apt install -y pip pkg-config`.
 
 You can skip the entire next section about Poetry and jump right to [Using Cashu](#using-cashu).
 
diff --git a/cashu/mint/ledger.py b/cashu/mint/ledger.py
index 944c653..5419aed 100644
--- a/cashu/mint/ledger.py
+++ b/cashu/mint/ledger.py
@@ -237,10 +237,13 @@ class Ledger:
     async def mint(self, B_s: List[PublicKey], amounts: List[int], payment_hash=None):
         """Mints a promise for coins for B_."""
         # check if lightning invoice was paid
-        if LIGHTNING and (
-            payment_hash and not await self._check_lightning_invoice(payment_hash)
-        ):
-            raise Exception("Lightning invoice not paid yet.")
+        if LIGHTNING:
+            try:
+                paid = await self._check_lightning_invoice(payment_hash)
+            except:
+                raise Exception("could not check invoice.")
+            if not paid:
+                raise Exception("Lightning invoice not paid yet.")
 
         for amount in amounts:
             if amount not in [2**i for i in range(MAX_ORDER)]: