diff --git a/Dockerfile b/Dockerfile
index a0dc037..71c6244 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -43,6 +43,8 @@ ENV BITCOIN_PRICE_URL="https://api.kraken.com/0/public/Ticker?pair=xbtusd"
 ENV BITCOIN_PRICE_JSON_PATH="result.XXBTZUSD.c[0]"
 ENV BITCOIN_PAYEE_NAME="Bitcoin Price Change"
 
+VOLUME ./cache
+
 # Copy the current directory contents into the container at /usr/src/app
 COPY --chown=node:node . .
 
diff --git a/track-investments.js b/track-investments.js
index 539a522..19e5ed5 100644
--- a/track-investments.js
+++ b/track-investments.js
@@ -22,7 +22,8 @@ const getCredentials = async () => {
   const pw = auth.split(':')[1];
 
   const data = `${username}:${pw}`;
-  fs.writeFileSync('simplefin.credentials', data);
+  const cache = process.env.ACTUAL_CACHE_DIR || './cache';
+  fs.writeFileSync(cache + '/simplefin.credentials', data);
   console.log('SimpleFIN credentials:', data);
   return data;
 };