Unchecked compiler warning

I have the following test code and get an error:

G:\BCIS 3680\Problem 2\src\my\Problem2\TestError.java:14: warning:
[unchecked] unchecked call to addElement(E) as a member of the raw
type java.util.Vector

Can anyone please explain to me what is wrong with the code? I don't
get it.

package my.Problem2;

import java.util.Vector;

class TestError {
protected Vector canoes = null;

public TestError() {
canoes = new Vector();
}

public synchronized void addRow(Canoe c) {
boolean addedRow = false;
canoes.addElement(c);
}
}

Thanks

.