diff --git a/lib/postgresql_interface.js b/lib/postgresql_interface.js
index d21fad3f..b128d9b5 100644
--- a/lib/postgresql_interface.js
+++ b/lib/postgresql_interface.js
@@ -177,6 +177,7 @@ function billsAndTxs(client, session, cb) {
 // lamassu-machine and lamassu-server and need to stay in sync.
 function bitcoinFractionalDigits(amount) {
   var log = Math.floor(Math.log(amount) / Math.log(10));
+  if (log < -8) log = -8;
   return (log > 0) ? 2 : 2 - log;
 }