diff --git a/server_extensions_extra/src/main/java/com/generalbytes/batm/server/extensions/extra/bitcoin/sources/yahoo/YahooFinanceRateSource.java b/server_extensions_extra/src/main/java/com/generalbytes/batm/server/extensions/extra/bitcoin/sources/yahoo/YahooFinanceRateSource.java
index 87bc1e3..66db9bf 100644
--- a/server_extensions_extra/src/main/java/com/generalbytes/batm/server/extensions/extra/bitcoin/sources/yahoo/YahooFinanceRateSource.java
+++ b/server_extensions_extra/src/main/java/com/generalbytes/batm/server/extensions/extra/bitcoin/sources/yahoo/YahooFinanceRateSource.java
@@ -36,7 +36,7 @@ public class YahooFinanceRateSource implements IRateSource{
     private static final Logger log = LoggerFactory.getLogger(YahooFinanceRateSource.class);
 
 
-    private static HashMap<String,BigDecimal> rateAmounts = new HashMap<String, BigDecimal>();
+    private static final HashMap<String,BigDecimal> rateAmounts = new HashMap<String, BigDecimal>();
     private static HashMap<String,Long> rateTimes = new HashMap<String, Long>();
     private static final long MAXIMUM_ALLOWED_TIME_OFFSET = 10 * 60 * 1000; //10 min