diff --git a/final/eventloop/signal_monitor.cpp b/final/eventloop/signal_monitor.cpp
index c3e05e9f..d6b43147 100644
--- a/final/eventloop/signal_monitor.cpp
+++ b/final/eventloop/signal_monitor.cpp
@@ -42,7 +42,7 @@ namespace finalcut
 std::map<int, SignalMonitor*> SignalMonitor::signal_monitors{};
 
 
-class SigactionImpl
+class SignalMonitor::SigactionImpl
 {
   public:
     // Destructor
@@ -69,11 +69,11 @@ auto SignalMonitor::getSigactionImpl() -> SigactionImpl*
 
 // SigactionImpl inline functions
 //----------------------------------------------------------------------
-inline auto SigactionImpl::getSigaction() const -> const struct sigaction*
+inline auto SignalMonitor::SigactionImpl::getSigaction() const -> const struct sigaction*
 { return &old_sig_action; }
 
 //----------------------------------------------------------------------
-inline auto SigactionImpl::getSigaction() -> struct sigaction*
+inline auto SignalMonitor::SigactionImpl::getSigaction() -> struct sigaction*
 { return &old_sig_action; }
 
 // SignalMonitor constructors and destructor
diff --git a/final/eventloop/signal_monitor.h b/final/eventloop/signal_monitor.h
index 6b923f31..6d673845 100644
--- a/final/eventloop/signal_monitor.h
+++ b/final/eventloop/signal_monitor.h
@@ -45,8 +45,6 @@
 namespace finalcut
 {
 
-class SigactionImpl;
-
 class SignalMonitor final : public Monitor
 {
   public:
@@ -64,6 +62,8 @@ class SignalMonitor final : public Monitor
     void trigger (short) override;
 
   private:
+    class SigactionImpl;
+
     // Disable copy assignment operator (=)
     auto operator = (const SignalMonitor&) -> SignalMonitor& = delete;