diff --git a/phpthread.go b/phpthread.go
index a941de9348..1fdb4f7bc6 100644
--- a/phpthread.go
+++ b/phpthread.go
@@ -34,6 +34,12 @@ type threadHandler interface {
 	afterScriptExecution(exitStatus int)
 	context() context.Context
 	frankenPHPContext() *frankenPHPContext
+	// drain is a hook called by drainWorkerThreads right before drainChan is
+	// closed. Handlers that need to wake up a thread parked in a blocking C
+	// call (e.g. by closing a stop pipe) plug their signal in here. All
+	// current handlers are no-ops; this is the seam later handler types use
+	// without having to modify drainWorkerThreads.
+	drain()
 }
 
 func newPHPThread(threadIndex int) *phpThread {
diff --git a/threadinactive.go b/threadinactive.go
index b5d11fcdfc..e6de0b4be5 100644
--- a/threadinactive.go
+++ b/threadinactive.go
@@ -58,3 +58,5 @@ func (handler *inactiveThread) context() context.Context {
 func (handler *inactiveThread) name() string {
 	return "Inactive PHP Thread"
 }
+
+func (handler *inactiveThread) drain() {}
diff --git a/threadregular.go b/threadregular.go
index 49db71106b..2f52963726 100644
--- a/threadregular.go
+++ b/threadregular.go
@@ -83,6 +83,8 @@ func (handler *regularThread) name() string {
 	return "Regular PHP Thread"
 }
 
+func (handler *regularThread) drain() {}
+
 func (handler *regularThread) waitForRequest() string {
 	// max_requests reached: restart the thread to clean up all ZTS state
 	if maxRequestsPerThread > 0 && handler.requestCount >= maxRequestsPerThread {
diff --git a/threadtasks_test.go b/threadtasks_test.go
index 2e74b12e93..d6954d161c 100644
--- a/threadtasks_test.go
+++ b/threadtasks_test.go
@@ -79,6 +79,8 @@ func (handler *taskThread) name() string {
 	return "Task PHP Thread"
 }
 
+func (handler *taskThread) drain() {}
+
 func (handler *taskThread) waitForTasks() {
 	for {
 		select {
diff --git a/threadworker.go b/threadworker.go
index 0fb315d1dc..21e1034805 100644
--- a/threadworker.go
+++ b/threadworker.go
@@ -105,6 +105,8 @@ func (handler *workerThread) name() string {
 	return "Worker PHP Thread - " + handler.worker.fileName
 }
 
+func (handler *workerThread) drain() {}
+
 func setupWorkerScript(handler *workerThread, worker *worker) {
 	metrics.StartWorker(worker.name)
 
diff --git a/worker.go b/worker.go
index c97cc4a3a7..5888c0e462 100644
--- a/worker.go
+++ b/worker.go
@@ -189,6 +189,7 @@ func drainWorkerThreads() []*phpThread {
 				continue
 			}
 
+			thread.handler.drain()
 			close(thread.drainChan)
 			drainedThreads = append(drainedThreads, thread)