Index: src/test/java/org/quartz/CronExpressionTest.java
===================================================================
--- src/test/java/org/quartz/CronExpressionTest.java	(revision 690)
+++ src/test/java/org/quartz/CronExpressionTest.java	(working copy)
@@ -15,8 +15,10 @@
  */
 package org.quartz;
 
+import java.io.*;
 import java.text.ParseException;
 import java.util.Calendar;
+import java.util.Date;
 import java.util.TimeZone;
 
 public class CronExpressionTest extends SerializationTestSupport {
@@ -78,4 +80,24 @@
         cal.set(2005, Calendar.JUNE, 1, 10, 14, 0);
         assertFalse(cronExpression.isSatisfiedBy(cal.getTime()));
     }
+
+    /*
+     * QUARTZ-571: Showing that expressions with months correctly serialize.
+     */
+    public void testQuartz571() throws Exception {
+        CronExpression cronExpression = new CronExpression("19 15 10 4 Apr ? ");
+
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ObjectOutputStream oos = new ObjectOutputStream(baos);
+        oos.writeObject(cronExpression);
+        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
+        ObjectInputStream ois = new ObjectInputStream(bais);
+        CronExpression newExpression = (CronExpression) ois.readObject();
+
+        assertEquals(newExpression.getCronExpression(), cronExpression.getCronExpression());
+
+        // if broken, this will throw an exception
+        newExpression.getNextValidTimeAfter(new Date());
+    }
+
 }
Index: src/java/org/quartz/CronExpression.java
===================================================================
--- src/java/org/quartz/CronExpression.java	(revision 690)
+++ src/java/org/quartz/CronExpression.java	(working copy)
@@ -241,9 +241,9 @@
             throw new IllegalArgumentException("cronExpression cannot be null");
         }
         
-        this.cronExpression = cronExpression;
+        this.cronExpression = cronExpression.toUpperCase(Locale.US);
         
-        buildExpression(cronExpression.toUpperCase(Locale.US));
+        buildExpression(this.cronExpression);
     }
     
     /**
@@ -1518,4 +1518,4 @@
     public int value;
 
     public int pos;
-}
\ No newline at end of file
+}