Index: src/XMPPJSONFileStorage.m
==================================================================
--- src/XMPPJSONFileStorage.m
+++ src/XMPPJSONFileStorage.m
@@ -37,11 +37,12 @@
 @implementation XMPPJSONFileStorage
 - init
 {
 	Class c = isa;
 	[self release];
-	@throw [OFNotImplementedException exceptionWithClass: c];
+	@throw [OFNotImplementedException exceptionWithClass: c
+						    selector: _cmd];
 }
 
 - initWithFile: (OFString*)file_
 {
 	self = [super init];
@@ -101,12 +102,15 @@
 		}
 
 		iter = iter2;
 	}
 
-	[iter setObject: object
-		 forKey: [pathComponents lastObject]];
+	if (object != nil)
+		[iter setObject: object
+			 forKey: [pathComponents lastObject]];
+	else
+		[iter removeObjectForKey: [pathComponents lastObject]];
 }
 
 - (id)XMPP_objectForPath: (OFString*)path
 {
 	OFArray *pathComponents = [path componentsSeparatedByString: @"."];

Index: src/XMPPRoster.m
==================================================================
--- src/XMPPRoster.m
+++ src/XMPPRoster.m
@@ -131,10 +131,11 @@
 	if ([connection supportsRosterVersioning]) {
 		OFString *ver =
 		    [[rosterElement attributeForName: @"ver"] stringValue];
 		[dataStorage setStringValue: ver
 				    forPath: @"roster.ver"];
+		[dataStorage save];
 	}
 
 	[delegates broadcastSelector: @selector(
 					  roster:didReceiveRosterItem:)
 			  withObject: self
@@ -226,10 +227,13 @@
 {
 	if ([connection supportsRosterVersioning]) {
 		OFMutableDictionary *items = [[[dataStorage dictionaryForPath:
 		    @"roster.items"] mutableCopy] autorelease];
 
+		if (items == nil)
+			items = [OFMutableDictionary dictionary];
+
 		if (![[rosterItem subscription] isEqual: @"remove"]) {
 			OFMutableDictionary *item = [OFMutableDictionary
 			    dictionaryWithKeysAndObjects:
 			    @"JID", [[rosterItem JID] bareJID],
 			    @"subscription", [rosterItem subscription],
@@ -340,10 +344,11 @@
 	if ([connection supportsRosterVersioning]) {
 		OFString *ver =
 		    [[rosterElement attributeForName: @"ver"] stringValue];
 		[dataStorage setStringValue: ver
 				    forPath: @"roster.ver"];
+		[dataStorage save];
 	}
 
 	[delegates broadcastSelector: @selector(rosterWasReceived:)
 			  withObject: self];
 }

Index: tests/test.m
==================================================================
--- tests/test.m
+++ tests/test.m
@@ -30,10 +30,11 @@
 #import "XMPPStanza.h"
 #import "XMPPIQ.h"
 #import "XMPPMessage.h"
 #import "XMPPPresence.h"
 #import "XMPPRoster.h"
+#import "XMPPJSONFileStorage.h"
 
 @interface AppDelegate: OFObject
 #ifdef OF_HAVE_OPTIONAL_PROTOCOLS
     <OFApplicationDelegate, XMPPConnectionDelegate, XMPPRosterDelegate>
 #endif
@@ -90,14 +91,19 @@
 	assert([[elem XMLString] isEqual: [stanza XMLString]]);
 	assert(([[OFString stringWithFormat: @"%@, %@, %@, %@",
 	    [[stanza from] fullJID], [[stanza to] fullJID], [stanza type],
 	    [stanza ID]] isEqual: @"bob@localhost, alice@localhost, get, 42"]));
 
-	conn = [[XMPPConnection alloc] init];
-	roster = [[XMPPRoster alloc] initWithConnection: conn];
 
+	conn = [[XMPPConnection alloc] init];
 	[conn addDelegate: self];
+
+	XMPPJSONFileStorage *storage =
+	    [[XMPPJSONFileStorage alloc] initWithFile: @"storage.json"];
+	[conn setDataStorage: storage];
+
+	roster = [[XMPPRoster alloc] initWithConnection: conn];
 	[roster addDelegate: self];
 
 	if ([arguments count] != 3) {
 		of_log(@"Invalid count of command line arguments!");
 		[OFApplication terminateWithStatus: 1];