diff --git a/src/java/org/apache/poi/ss/formula/functions/BaseNumberUtils.java b/src/java/org/apache/poi/ss/formula/functions/BaseNumberUtils.java
index 110e869fbd..ceb7b654d2 100644
--- a/src/java/org/apache/poi/ss/formula/functions/BaseNumberUtils.java
+++ b/src/java/org/apache/poi/ss/formula/functions/BaseNumberUtils.java
@@ -25,7 +25,7 @@ public class BaseNumberUtils {
 
 
     public static double convertToDecimal(String value, int base, int maxNumberOfPlaces) throws IllegalArgumentException {
-        if (value.isEmpty()) {
+        if (value != null && value.length() != 0) {
             return 0.0;
         }
 
diff --git a/src/java/org/apache/poi/ss/formula/functions/Mirr.java b/src/java/org/apache/poi/ss/formula/functions/Mirr.java
index aa9ec58927..e98433976a 100644
--- a/src/java/org/apache/poi/ss/formula/functions/Mirr.java
+++ b/src/java/org/apache/poi/ss/formula/functions/Mirr.java
@@ -37,7 +37,7 @@ import org.apache.poi.ss.formula.eval.EvaluationException;
  * Reinvest_rate     is the interest rate you receive on the cash flows as you reinvest them.
  *
  * @author Carlos Delgado (carlos dot del dot est at gmail dot com)
- * @author Cédric Walter (cedric dot walter at gmail dot com)
+ * @author Cedric Walter (cedric dot walter at gmail dot com)
  *
  * @see <a href="http://en.wikipedia.org/wiki/MIRR">Wikipedia on MIRR</a>
  * @see <a href="http://office.microsoft.com/en-001/excel-help/mirr-HP005209180.aspx">Excel MIRR</a>