diff --git a/repos/base-hw/src/core/include/kernel/core_interface.h b/repos/base-hw/src/core/include/kernel/core_interface.h
index 4f49cea58..09b1a19c4 100644
--- a/repos/base-hw/src/core/include/kernel/core_interface.h
+++ b/repos/base-hw/src/core/include/kernel/core_interface.h
@@ -58,6 +58,7 @@ namespace Kernel
 	constexpr Call_arg call_id_new_irq()                { return 32; }
 	constexpr Call_arg call_id_delete_irq()             { return 33; }
 	constexpr Call_arg call_id_thread_quota()           { return 34; }
+	constexpr Call_arg call_id_ack_irq()                { return 35; }
 
 	/**
 	 * Create a domain
@@ -376,6 +377,16 @@ namespace Kernel
 		return call(call_id_new_irq(), (Call_arg) p, irq_nr, signal_context_id);
 	}
 
+	/**
+	 * Acknowledge interrupt
+	 *
+	 * \param irq  pointer to interrupt kernel object
+	 */
+	inline void ack_irq(User_irq * const irq)
+	{
+		call(call_id_ack_irq(), (Call_arg) irq);
+	}
+
 	/**
 	 * Destruct an interrupt object
 	 *
diff --git a/repos/base-hw/src/core/include/kernel/irq.h b/repos/base-hw/src/core/include/kernel/irq.h
index 83ec010da..1d753d23b 100644
--- a/repos/base-hw/src/core/include/kernel/irq.h
+++ b/repos/base-hw/src/core/include/kernel/irq.h
@@ -90,10 +90,7 @@ class Kernel::Irq : public Object_pool<Irq>::Item
 };
 
 
-class Kernel::User_irq
-:
-	public Kernel::Irq,
-	public Signal_ack_handler
+class Kernel::User_irq : public Kernel::Irq
 {
 	private:
 
@@ -104,32 +101,18 @@ class Kernel::User_irq
 		 */
 		static Irq::Pool * _pool();
 
-
-		/************************
-		 ** Signal_ack_handler **
-		 ************************/
-
-		void _signal_acknowledged() { enable(); }
-
 	public:
 
 		/**
-		 * Constructor
-		 *
-		 * \param irq_id  kernel name of the interrupt
+		 * Construct object that signals interrupt 'irq' via signal 'context'
 		 */
-		User_irq(unsigned const irq_id, Signal_context &context)
-		: Irq(irq_id, *_pool()), _context(context)
-		{
-			disable();
-			_context.ack_handler(this);
-		}
+		User_irq(unsigned const irq, Signal_context &context)
+		: Irq(irq, *_pool()), _context(context) { disable(); }
 
-		~User_irq()
-		{
-			_context.ack_handler(nullptr);
-			disable();
-		}
+		/**
+		 * Destructor
+		 */
+		~User_irq() { disable(); }
 
 		/**
 		 * Handle occurence of the interrupt
@@ -141,12 +124,10 @@ class Kernel::User_irq
 		}
 
 		/**
-		 * Handle occurence of an interrupt
-		 *
-		 * \param irq_id  kernel name of targeted interrupt
+		 * Handle occurence of interrupt 'irq'
 		 */
-		static User_irq * object(unsigned const irq_id) {
-			return dynamic_cast<User_irq*>(_pool()->object(irq_id)); }
+		static User_irq * object(unsigned const irq) {
+			return dynamic_cast<User_irq*>(_pool()->object(irq)); }
 };
 
 #endif /* _KERNEL__IRQ_H_ */
diff --git a/repos/base-hw/src/core/include/kernel/thread.h b/repos/base-hw/src/core/include/kernel/thread.h
index c802bf84f..0a4cb7529 100644
--- a/repos/base-hw/src/core/include/kernel/thread.h
+++ b/repos/base-hw/src/core/include/kernel/thread.h
@@ -245,6 +245,7 @@ class Kernel::Thread
 		void _call_route_thread_event();
 		void _call_new_irq();
 		void _call_delete_irq();
+		void _call_ack_irq();
 
 
 		/***************************
diff --git a/repos/base-hw/src/core/irq_session_component.cc b/repos/base-hw/src/core/irq_session_component.cc
index 891e7bea5..f50105d43 100644
--- a/repos/base-hw/src/core/irq_session_component.cc
+++ b/repos/base-hw/src/core/irq_session_component.cc
@@ -31,7 +31,10 @@ unsigned Irq_session_component::_find_irq_number(const char * const args)
 
 void Irq_session_component::ack_irq()
 {
-	Kernel::ack_signal(_sig_cap.dst());
+	using Kernel::User_irq;
+	if (!_sig_cap.valid()) { return; }
+	User_irq * const kirq = reinterpret_cast<User_irq*>(&_kernel_object);
+	Kernel::ack_irq(kirq);
 }
 
 
diff --git a/repos/base-hw/src/core/kernel/thread.cc b/repos/base-hw/src/core/kernel/thread.cc
index 5ef9e6e96..69eb94399 100644
--- a/repos/base-hw/src/core/kernel/thread.cc
+++ b/repos/base-hw/src/core/kernel/thread.cc
@@ -713,6 +713,10 @@ void Thread::_call_new_irq()
 }
 
 
+void Thread::_call_ack_irq() {
+	reinterpret_cast<User_irq*>(user_arg_1())->enable(); }
+
+
 void Thread::_call_delete_irq() {
 	reinterpret_cast<User_irq*>(user_arg_1())->~User_irq(); }
 
@@ -794,6 +798,7 @@ void Thread::_call()
 	case call_id_pause_thread():           _call_pause_thread(); return;
 	case call_id_new_irq():                _call_new_irq(); return;
 	case call_id_delete_irq():             _call_delete_irq(); return;
+	case call_id_ack_irq():                _call_ack_irq(); return;
 	default:
 		PWRN("%s -> %s: unknown kernel call", pd_label(), label());
 		_stop();