diff --git a/core/sip/wheeltimer.cpp b/core/sip/wheeltimer.cpp
index 16635148..cafaf1d7 100644
--- a/core/sip/wheeltimer.cpp
+++ b/core/sip/wheeltimer.cpp
@@ -112,52 +112,48 @@ void _wheeltimer::process_current_timers(timer_list& list, std::unique_lock<std:
 {
     while (!list.empty()) {
 	auto* t = list.front();
-	list.pop_front();
+
+	t->disarm(); // removes it from list
 
 	// safe to unlock now
 	lock.unlock();
 
-	t->list = NULL;
-	t->disarm();
-
 	t->fire();
 
 	lock.lock();
     }
 }
 
-void _wheeltimer::place_timer(timer* t)
+uint64_t _wheeltimer::get_timer_bucket(timer* t)
 {
-    t->arm();
-
     uint64_t exp = t->get_absolute_expiry();
 
     // scale expiry based on resolution: this is the bucket index
-    exp = ((exp / resolution) + 1) * resolution;
+    uint64_t bucket = ((exp / resolution) + 1) * resolution;
 
     // if expiry is too soon or in the past, put the timer in the next bucket up
     auto now = gettimeofday_us();
-    if (exp <= now)
-	exp = ((now / resolution) + 1) * resolution;
+    if (bucket <= now)
+	bucket = ((now / resolution) + 1) * resolution;
+
+    return bucket;
+}
 
-    add_timer_to_bucket(t, exp);
+void _wheeltimer::place_timer(timer* t)
+{
+    t->arm();
+    uint64_t bucket = get_timer_bucket(t);
+    add_timer_to_bucket(t, bucket);
 }
 
 void _wheeltimer::add_timer_to_bucket(timer* t, uint64_t bucket)
 {
-    auto& b = buckets[bucket];
-    t->list = &b;
-    b.push_front(t);
-    t->pos = b.begin();
+    t->link(buckets[bucket]);
 }
 
 void _wheeltimer::delete_timer(timer* t)
 {
-    if (t->list) {
-	t->list->erase(t->pos);
-	t->list = NULL;
-    }
-
+    t->disarm();
     delete t;
 }
 
diff --git a/core/sip/wheeltimer.h b/core/sip/wheeltimer.h
index 813c0af5..f28b9373 100644
--- a/core/sip/wheeltimer.h
+++ b/core/sip/wheeltimer.h
@@ -48,11 +48,11 @@ typedef std::map<uint64_t, timer_list> timer_buckets;
 
 class timer
 {
-public:
     // for fast removal:
     timer_list::iterator pos;
     timer_list* list;
 
+public:
     timer() 
 	: list(NULL), expires(0), expires_rel(0)
     {}
@@ -69,19 +69,28 @@ public:
 
     virtual void fire()=0;
 
-    // returns true if timer was not armed before
-    // return false and does nothing otherwise
-    bool arm()
+    void arm()
     {
 	if (expires)
-	    return false;
+	    return;
 	expires = expires_rel + gettimeofday_us();
-	return true;
+    }
+
+    void link(timer_list& new_list)
+    {
+	list = &new_list;
+	list->push_front(this);
+	pos = list->begin();
     }
 
     void disarm()
     {
 	expires = 0;
+
+	if (list) {
+	    list->erase(pos);
+	    list = NULL;
+	}
     }
 
     // microseconds
@@ -120,6 +129,7 @@ class _wheeltimer:
     void place_timer(timer* t);
 
     void add_timer_to_bucket(timer* t, uint64_t);
+    uint64_t get_timer_bucket(timer* t);
     void delete_timer(timer* t);
 
     void process_current_timers(timer_list&, std::unique_lock<std::mutex>&);