diff --git a/src/timer.cpp b/src/timer.cpp
index 9c37fa2..ed27891 100644
--- a/src/timer.cpp
+++ b/src/timer.cpp
@@ -7,8 +7,17 @@
 uint64_t sc::timer::next_id = 0;
 std::mutex sc::timer::mutex;
 
-sc::timer::timer(void(*callback)(union sigval), double time, bool repeat)
-    : _id {}, _time {time}, _repeat {repeat}
+void sc::timer::callback(union sigval sv) {
+    timer* self = reinterpret_cast<timer*>(sv.sival_ptr);
+    self->_expired_func(self, self->_context);
+}
+
+sc::timer::timer(void(*expired_func)(timer*, void*),
+                 double time,
+                 bool repeat,
+                 void* context)
+    : _id {}, _time {time}, _repeat {repeat},
+      _expired_func {expired_func}, _context {context}
 {
     {
         std::lock_guard<std::mutex> lock {mutex};
@@ -17,7 +26,7 @@ sc::timer::timer(void(*callback)(union sigval), double time, bool repeat)
     struct sigevent se;
     se.sigev_notify = SIGEV_THREAD;
     se.sigev_value.sival_int = 0;
-    se.sigev_value.sival_ptr = &_id;
+    se.sigev_value.sival_ptr = this;
     se.sigev_notify_function = callback;
     se.sigev_notify_attributes = nullptr;
     throw_if_min1_msg(timer_create(CLOCK_MONOTONIC, &se, &_tid), "could not create timer");
diff --git a/src/timer.hpp b/src/timer.hpp
index f28c5ee..030be04 100644
--- a/src/timer.hpp
+++ b/src/timer.hpp
@@ -11,19 +11,28 @@ namespace sc {
         static std::mutex mutex;
 
         timer_t _tid;
-        uint64_t _id;
-        double _time;
-        bool _repeat;
+        uint64_t _id {};
+        double _time {};
+        bool _repeat {};
+        void (*_expired_func)(timer* self, void* context);
+        void* _context {};
+
+        static void callback(union sigval);
 
         public:
-            timer(void(*callback)(union sigval), double time, bool repeat = false);
+            timer(void(*expired_func)(timer*, void*),
+                  double time,
+                  bool repeat,
+                  void* context);
             ~timer();
 
+            uint64_t id() const { return _id; }
+            double time() const { return _time; }
+            bool repeat() const { return _repeat; }
+
+            bool is_armed() const;
             void time_left(struct itimerspec& cur_value) const;
             double time_left() const;
-            double time() const { return _time; }
-            bool is_armed() const;
-            bool repeat() const { return _repeat; }
     };
 
 }