diff --git a/programs/mutant-5/swen90006/passbook/PassBook.java b/programs/mutant-5/swen90006/passbook/PassBook.java
index bc24cb4698d81bba0e476b9cb1b5e595c9a8f3eb..9d99f0b8d5d9b728b0c39ba7a398cfb6901c5f2a 100644
--- a/programs/mutant-5/swen90006/passbook/PassBook.java
+++ b/programs/mutant-5/swen90006/passbook/PassBook.java
@@ -198,14 +198,14 @@ public class PassBook
     {
  	//check that the session ID exists
 	String passbookUsername = userIDs.get(sessionID);
-	if (passbookUsername == null) {
+	if (passbookUsername != null) {
 	    throw new InvalidSessionIDException(sessionID);
 	}
 	else if (!Arrays.asList(VALID_URL_PROTOCOLS).contains(url.getProtocol())) {
 	    throw new MalformedURLException(passbookUsername);
 	}
 
-	PasswordTable pt = details.get(sessionID);
+	PasswordTable pt = details.get(passbookUsername);
 	if (urlUsername == null || urlPassword == null) {
 	    pt.remove(url);
 	}