diff --git a/src/main.cc b/src/main.cc
index 0760c6b664..ffcce06bc3 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -674,6 +674,9 @@ int main(int argc, char** argv)
 	broker_mgr->InitPostScript();
 	timer_mgr->InitPostScript();
 
+	if ( zeek::supervisor_mgr )
+		zeek::supervisor_mgr->InitPostScript();
+
 	if ( options.print_plugins )
 		{
 		bool success = show_plugins(options.print_plugins);
diff --git a/src/supervisor/Supervisor.cc b/src/supervisor/Supervisor.cc
index b6e157c1a3..4ef342ffb7 100644
--- a/src/supervisor/Supervisor.cc
+++ b/src/supervisor/Supervisor.cc
@@ -10,6 +10,7 @@
 #include <cstdarg>
 #include <sstream>
 
+#include "iosource/Manager.h"
 #include "Supervisor.h"
 #include "Reporter.h"
 #include "DebugLogger.h"
@@ -160,7 +161,6 @@ Supervisor::Supervisor(Supervisor::Config cfg, StemState ss)
 	{
 	DBG_LOG(DBG_SUPERVISOR, "forked stem process %d", stem_pid);
 	setsignal(SIGCHLD, supervisor_signal_handler);
-	SetIdle(true);
 
 	int status;
 	auto res = waitpid(stem_pid, &status, WNOHANG);
@@ -197,6 +197,9 @@ Supervisor::~Supervisor()
 		return;
 		}
 
+	iosource_mgr->UnregisterFd(signal_flare.FD(), this);
+	iosource_mgr->UnregisterFd(stem_pipe->InFD(), this);
+
 	DBG_LOG(DBG_SUPERVISOR, "shutdown, killing stem process %d", stem_pid);
 
 	auto kill_res = kill(stem_pid, SIGTERM);
@@ -352,16 +355,16 @@ void Supervisor::HandleChildSignal()
 		}
 	}
 
-void Supervisor::GetFds(iosource::FD_Set* read, iosource::FD_Set* write,
-                        iosource::FD_Set* except)
+void Supervisor::InitPostScript()
 	{
-	read->Insert(signal_flare.FD());
-	read->Insert(stem_pipe->InFD());
+	iosource_mgr->Register(this);
+	iosource_mgr->RegisterFd(signal_flare.FD(), this);
+	iosource_mgr->RegisterFd(stem_pipe->InFD(), this);
 	}
 
-double Supervisor::NextTimestamp(double* local_network_time)
+double Supervisor::GetNextTimeout()
 	{
-	return timer_mgr->Time();
+	return -1;
 	}
 
 void Supervisor::Process()
diff --git a/src/supervisor/Supervisor.h b/src/supervisor/Supervisor.h
index 32b07e5aff..36d00f1808 100644
--- a/src/supervisor/Supervisor.h
+++ b/src/supervisor/Supervisor.h
@@ -285,6 +285,12 @@ public:
 	 */
 	~Supervisor();
 
+	/**
+	 * Perform some initialization that needs to happen after scripts are loaded
+	 * and the IOSource manager is created.
+	 */
+	void InitPostScript();
+
 	/**
 	 * @return the process ID of the Stem.
 	 */
@@ -347,11 +353,7 @@ public:
 private:
 
 	// IOSource interface overrides:
-	void GetFds(iosource::FD_Set* read, iosource::FD_Set* write,
-	            iosource::FD_Set* except) override;
-
-	double NextTimestamp(double* local_network_time) override;
-
+	double GetNextTimeout() override;
 	void Process() override;
 
 	size_t ProcessMessages();