diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/FlashMap.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/FlashMap.java
index 03a2ecfdf0..fa58cd5e78 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/FlashMap.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/FlashMap.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@ import org.springframework.util.MultiValueMap;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
+
 /**
  * A FlashMap provides a way for one request to store attributes intended for
  * use in another. This is most commonly needed when redirecting from one URL
@@ -50,11 +51,9 @@ public final class FlashMap extends HashMap<String, Object> implements Comparabl
 
 	private String targetRequestPath;
 
-	private final MultiValueMap<String, String> targetRequestParams = new LinkedMultiValueMap<String, String>();
-
-	private long expirationStartTime;
+	private final MultiValueMap<String, String> targetRequestParams = new LinkedMultiValueMap<String, String>(4);
 
-	private int timeToLive;
+	private long expirationTime = -1;
 
 
 	/**
@@ -112,8 +111,25 @@ public final class FlashMap extends HashMap<String, Object> implements Comparabl
 	 * @param timeToLive the number of seconds before expiration
 	 */
 	public void startExpirationPeriod(int timeToLive) {
-		this.expirationStartTime = System.currentTimeMillis();
-		this.timeToLive = timeToLive;
+		this.expirationTime = System.currentTimeMillis() + timeToLive * 1000;
+	}
+
+	/**
+	 * Set the expiration time for the FlashMap. This is provided for serialization
+	 * purposes but can also be used instead {@link #startExpirationPeriod(int)}.
+	 * @since 4.2
+	 */
+	public void setExpirationTime(long expirationTime) {
+		this.expirationTime = expirationTime;
+	}
+
+	/**
+	 * Return the expiration time for the FlashMap or -1 if the expiration
+	 * period has not started.
+	 * @since 4.2
+	 */
+	public long getExpirationTime() {
+		return this.expirationTime;
 	}
 
 	/**
@@ -121,8 +137,7 @@ public final class FlashMap extends HashMap<String, Object> implements Comparabl
 	 * elapsed time since the call to {@link #startExpirationPeriod}.
 	 */
 	public boolean isExpired() {
-		return (this.expirationStartTime != 0 &&
-				(System.currentTimeMillis() - this.expirationStartTime > this.timeToLive * 1000));
+		return (this.expirationTime != -1 && System.currentTimeMillis() > this.expirationTime);
 	}
 
 
@@ -167,11 +182,8 @@ public final class FlashMap extends HashMap<String, Object> implements Comparabl
 
 	@Override
 	public String toString() {
-		StringBuilder sb = new StringBuilder();
-		sb.append("FlashMap [attributes=").append(super.toString());
-		sb.append(", targetRequestPath=").append(this.targetRequestPath);
-		sb.append(", targetRequestParams=").append(this.targetRequestParams).append("]");
-		return sb.toString();
+		return "FlashMap [attributes=" + super.toString() + ", targetRequestPath=" +
+				this.targetRequestPath + ", targetRequestParams=" + this.targetRequestParams + "]";
 	}
 
 }