diff --git a/CppTimerCallback.h b/CppTimerCallback.h
index 7f56fc3..233bf97 100644
--- a/CppTimerCallback.h
+++ b/CppTimerCallback.h
@@ -3,35 +3,31 @@
 #include <stdio.h>
 #include "CppTimer.h"
 #include <unistd.h>
+#include <vector>
 
 // Demo which creates a callback interface as the abstract class "Runnable".
 // This then allows to register a callback.
 
 class CppTimerCallback : public CppTimer {
-
+    
 public:
-	class Runnable {
-	public:
-		virtual void run() = 0;
-	};
-
-	void registerEventRunnable(Runnable &h) {
-		cppTimerEventRunnable = &h;
-	}
-
-	void unregisterEventRunnable() {
-		cppTimerEventRunnable = NULL;
-	}
-	
-        void timerEvent() {
-		if (cppTimerEventRunnable) {
-			cppTimerEventRunnable->run();
-		}
+    class Runnable {
+    public:
+	virtual void run() = 0;
+    };
+    
+    void registerEventRunnable(Runnable &h) {
+	cppTimerEventRunnables.push_back(&h);
+    }
+    
+    void timerEvent() {
+	for(auto & r : cppTimerEventRunnables) {
+	    r->run();
 	}
+    }
 
 private:
-	Runnable* cppTimerEventRunnable = NULL;
-
+    std::vector<Runnable*> cppTimerEventRunnables;
 };
 
 
diff --git a/CppTimerStdFuncCallback.h b/CppTimerStdFuncCallback.h
index 2a52781..c353c25 100644
--- a/CppTimerStdFuncCallback.h
+++ b/CppTimerStdFuncCallback.h
@@ -4,6 +4,7 @@
 #include "CppTimer.h"
 #include <unistd.h>
 #include <functional>
+#include <vector>
 
 // This is a demo how to create a callback with std::function which allows
 // calling methods in other classes by registering a lambda function!
@@ -15,17 +16,17 @@ class CppTimerCallback : public CppTimer {
     using CallbackFunction = std::function<void(void)>;
 
     void registerEventCallback(CallbackFunction cf) {
-	callbackFunction = cf;
+	callbackFunctions.push_back(cf);
     }
     
     void timerEvent() {
-	if (nullptr != callbackFunction) {
-	    callbackFunction();
+	for(auto &cb : callbackFunctions) {
+	    cb();
 	}
     }
 
 private:
-    CallbackFunction callbackFunction = nullptr;
+    std::vector<CallbackFunction> callbackFunctions;
 };
 
 
diff --git a/demo_runnable.cpp b/demo_runnable.cpp
index 12e3e9f..1a4e1bb 100644
--- a/demo_runnable.cpp
+++ b/demo_runnable.cpp
@@ -32,10 +32,7 @@ int main( int, const char**) {
 	// do nothing and keep sleeping for 2 secs
 	std::this_thread::sleep_for(std::chrono::seconds(2));
 
-	demoTimer1.unregisterEventRunnable();
         demoTimer1.stop();
-
-	demoTimer2.unregisterEventRunnable();
         demoTimer2.stop();
 
 	printf("\n");