Re-adding an entry doesn't reset creation time when using lifespans

Hi,
I'm trying to migrate my application to Infinispan 5.1.0.FINAL but I have some problem.

My code uses put method passing lifespan parameter. In the new Infinispan version it seems that if I put an entry to the cache with a lifespan (e.g. 10 seconds) and then, after 5 seconds, I put the same entry with lifespan = 10 seconds, the lifespan is not overrided and the cache entry expires after 10 seconds from the first operation.

Here an example of code that reproduces the problem:

final Cache cache = .... // Obtain cache instance

// Put entry in cache
cache.put( "key_001", "v_001", 10, TimeUnit.SECONDS );

int x = 0;
while ( true ) {
// print cache entry every 500ms
System.out.println( ( x++ * 500 ) + "--->" + cache.get( "key_001" ) );

// every 5 seconds put the same entry with lifespan = 10 seconds
if ( x % 10 == 0 )

{ System.out.println("PING"); cache.put( "key_001", "v_001", 10, TimeUnit.SECONDS ); }

Thread.sleep( 500 );
}

The results is:
0--->v_001
500--->v_001
1000--->v_001
1500--->v_001
2000--->v_001
2500--->v_001
3000--->v_001
3500--->v_001
4000--->v_001
4500--->v_001
PING
5000--->v_001
5500--->v_001
6000--->v_001
6500--->v_001
7000--->v_001
7500--->v_001
8000--->v_001
8500--->v_001
9000--->v_001
9500--->v_001
PING
10000--->null
10500--->null
11000--->null
11500--->null
12000--->null
12500--->null
13000--->null
13500--->null
14000--->null
14500--->null
PING
15000--->v_001
15500--->v_001
16000--->v_001
16500--->v_001
17000--->v_001
17500--->v_001

With Infinispan 5.0.1 the result is
0--->v_001
500--->v_001
1000--->v_001
1500--->v_001
2000--->v_001
2500--->v_001
3000--->v_001
3500--->v_001
4000--->v_001
4500--->v_001
PING
5000--->v_001
5500--->v_001
6000--->v_001
6500--->v_001
7000--->v_001
7500--->v_001
8000--->v_001
8500--->v_001
9000--->v_001
9500--->v_001
PING
10000--->v_001
10500--->v_001
11000--->v_001
11500--->v_001
12000--->v_001
12500--->v_001
13000--->v_001
13500--->v_001
14000--->v_001
14500--->v_001
PING
15000--->v_001
15500--->v_001
16000--->v_001
16500--->v_001
17000--->v_001
17500--->v_001