diff --git a/src/DNS_Mgr.cc b/src/DNS_Mgr.cc
index 5599074b0d..903485a652 100644
--- a/src/DNS_Mgr.cc
+++ b/src/DNS_Mgr.cc
@@ -392,7 +392,6 @@ DNS_Mgr::DNS_Mgr(DNS_MgrMode arg_mode)
 	successful = 0;
 	failed = 0;
 	nb_dns = nullptr;
-	next_timestamp = -1.0;
 	}
 
 DNS_Mgr::~DNS_Mgr()
@@ -404,7 +403,7 @@ DNS_Mgr::~DNS_Mgr()
 	delete [] dir;
 	}
 
-void DNS_Mgr::Init()
+void DNS_Mgr::InitSource()
 	{
 	if ( did_init )
 		return;
@@ -440,7 +439,9 @@ void DNS_Mgr::Init()
 		nb_dns = nb_dns_init2(err, (struct sockaddr*)&ss);
 		}
 
-	if ( ! nb_dns )
+	if ( nb_dns )
+		iosource_mgr->RegisterFd(nb_dns_fd(nb_dns), this);
+	else
 		reporter->Warning("problem initializing NB-DNS: %s", err);
 
 	did_init = true;
@@ -460,11 +461,6 @@ void DNS_Mgr::InitPostScript()
 	// Registering will call Init()
 	iosource_mgr->Register(this, true);
 
-	// We never set idle to false, having the main loop only calling us from
-	// time to time. If we're issuing more DNS requests than we can handle
-	// in this way, we are having problems anyway ...
-	SetIdle(true);
-
 	const char* cache_dir = dir ? dir : ".";
 	cache_name = new char[strlen(cache_dir) + 64];
 	sprintf(cache_name, "%s/%s", cache_dir, ".zeek-dns-cache");
@@ -503,7 +499,7 @@ TableVal* DNS_Mgr::LookupHost(const char* name)
 	if ( mode == DNS_FAKE )
 		return fake_name_lookup_result(name);
 
-	Init();
+	InitSource();
 
 	if ( ! nb_dns )
 		return empty_addr_set();
@@ -558,7 +554,7 @@ TableVal* DNS_Mgr::LookupHost(const char* name)
 
 Val* DNS_Mgr::LookupAddr(const IPAddr& addr)
 	{
-	Init();
+	InitSource();
 
 	if ( mode != DNS_PRIME )
 		{
@@ -1078,7 +1074,7 @@ static void resolve_lookup_cb(DNS_Mgr::LookupCallback* callback,
 
 void DNS_Mgr::AsyncLookupAddr(const IPAddr& host, LookupCallback* callback)
 	{
-	Init();
+	InitSource();
 
 	if ( mode == DNS_FAKE )
 		{
@@ -1116,7 +1112,7 @@ void DNS_Mgr::AsyncLookupAddr(const IPAddr& host, LookupCallback* callback)
 
 void DNS_Mgr::AsyncLookupName(const string& name, LookupCallback* callback)
 	{
-	Init();
+	InitSource();
 
 	if ( mode == DNS_FAKE )
 		{
@@ -1154,7 +1150,7 @@ void DNS_Mgr::AsyncLookupName(const string& name, LookupCallback* callback)
 
 void DNS_Mgr::AsyncLookupNameText(const string& name, LookupCallback* callback)
 	{
-	Init();
+	InitSource();
 
 	if ( mode == DNS_FAKE )
 		{
@@ -1242,30 +1238,6 @@ void DNS_Mgr::IssueAsyncRequests()
 		}
 	}
 
-void DNS_Mgr::GetFds(iosource::FD_Set* read, iosource::FD_Set* write,
-                     iosource::FD_Set* except)
-	{
-	if ( ! nb_dns )
-		return;
-
-	read->Insert(nb_dns_fd(nb_dns));
-	}
-
-double DNS_Mgr::NextTimestamp(double* network_time)
-	{
-	if ( asyncs_timeouts.empty() )
-		// No pending requests.
-		return -1.0;
-
-	if ( next_timestamp < 0 )
-		// Store the timestamp to help prevent starvation by some other
-		// IOSource always trying to use the same timestamp
-		// (assuming network_time does actually increase).
-		next_timestamp = timer_mgr->Time();
-
-	return next_timestamp;
-	}
-
 void DNS_Mgr::CheckAsyncAddrRequest(const IPAddr& addr, bool timeout)
 	{
 	// Note that this code is a mirror of that for CheckAsyncHostRequest.
@@ -1369,7 +1341,7 @@ void DNS_Mgr::CheckAsyncHostRequest(const char* host, bool timeout)
 
 void DNS_Mgr::Flush()
 	{
-	DoProcess();
+	Process();
 
 	HostMap::iterator it;
 	for ( it = host_mappings.begin(); it != host_mappings.end(); ++it )
@@ -1389,13 +1361,15 @@ void DNS_Mgr::Flush()
 	text_mappings.clear();
 	}
 
-void DNS_Mgr::Process()
+double DNS_Mgr::GetNextTimeout()
 	{
-	DoProcess();
-	next_timestamp = -1.0;
+	if ( asyncs_timeouts.empty() )
+		return -1;
+
+	return network_time + DNS_TIMEOUT;
 	}
 
-void DNS_Mgr::DoProcess()
+void DNS_Mgr::Process()
 	{
 	if ( ! nb_dns )
 		return;
@@ -1513,3 +1487,8 @@ void DNS_Mgr::GetStats(Stats* stats)
 	stats->cached_texts = text_mappings.size();
 	}
 
+void DNS_Mgr::Terminate()
+	{
+	if ( nb_dns )
+		iosource_mgr->UnregisterFd(nb_dns_fd(nb_dns));
+	}
diff --git a/src/DNS_Mgr.h b/src/DNS_Mgr.h
index 00397f351f..6b5975f876 100644
--- a/src/DNS_Mgr.h
+++ b/src/DNS_Mgr.h
@@ -91,6 +91,8 @@ public:
 
 	void GetStats(Stats* stats);
 
+	void Terminate();
+
 protected:
 	friend class LookupCallback;
 	friend class DNS_Mgr_Request;
@@ -127,16 +129,11 @@ protected:
 	void CheckAsyncHostRequest(const char* host, bool timeout);
 	void CheckAsyncTextRequest(const char* host, bool timeout);
 
-	// Process outstanding requests.
-	void DoProcess();
-
 	// IOSource interface.
-	void GetFds(iosource::FD_Set* read, iosource::FD_Set* write,
-	                    iosource::FD_Set* except) override;
-	double NextTimestamp(double* network_time) override;
 	void Process() override;
-	void Init() override;
-	const char* Tag() override { return "DNS_Mgr"; }
+	void InitSource() override;
+	const char* Tag() override	{ return "DNS_Mgr"; }
+	double GetNextTimeout() override;
 
 	DNS_MgrMode mode;
 
@@ -241,7 +238,6 @@ protected:
 	unsigned long num_requests;
 	unsigned long successful;
 	unsigned long failed;
-	double next_timestamp;
 };
 
 extern DNS_Mgr* dns_mgr;
diff --git a/src/main.cc b/src/main.cc
index 00ad77a2e6..93d3c652c2 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -290,6 +290,7 @@ void terminate_bro()
 	input_mgr->Terminate();
 	thread_mgr->Terminate();
 	broker_mgr->Terminate();
+	dns_mgr->Terminate();
 
 	mgr.Drain();