diff --git a/phpmainthread_test.go b/phpmainthread_test.go
index d274991863..54722b0963 100644
--- a/phpmainthread_test.go
+++ b/phpmainthread_test.go
@@ -95,8 +95,9 @@ func TestTransitionThreadsWhileDoingRequests(t *testing.T) {
 	t.Cleanup(Shutdown)
 
 	var (
-		isDone atomic.Bool
-		wg     sync.WaitGroup
+		isDone        atomic.Bool
+		wg            sync.WaitGroup
+		transitionsWG sync.WaitGroup
 	)
 
 	numThreads := 10
@@ -122,8 +123,10 @@ func TestTransitionThreadsWhileDoingRequests(t *testing.T) {
 
 	// try all possible permutations of transition, transition every ms
 	transitions := allPossibleTransitions(worker1Path, worker2Path)
+	transitionsWG.Add(numThreads)
 	for i := range numThreads {
 		go func(thread *phpThread, start int) {
+			defer transitionsWG.Done()
 			for {
 				for j := start; j < len(transitions); j++ {
 					if isDone.Load() {
@@ -158,6 +161,9 @@ func TestTransitionThreadsWhileDoingRequests(t *testing.T) {
 	// we are finished as soon as all 1000 requests are done
 	wg.Wait()
 	isDone.Store(true)
+	// wait for transition goroutines to exit before Shutdown to avoid them
+	// racing with a subsequent test's initPHPThreads via mainThread.state
+	transitionsWG.Wait()
 }
 
 func TestFinishBootingAWorkerScript(t *testing.T) {