diff --git a/phpmainthread.go b/phpmainthread.go
index 5561cbd77..b1bcbd329 100644
--- a/phpmainthread.go
+++ b/phpmainthread.go
@@ -30,16 +30,18 @@ func initPHPThreads(numThreads int) error {
 	}
 	phpThreads = make([]*phpThread, numThreads)
 
-	if err := mainThread.start(); err != nil {
-		return err
-	}
-
 	// initialize all threads as inactive
+	// this needs to happen before starting the main thread
+	// since some extensions access environment variables on startup
 	for i := 0; i < numThreads; i++ {
 		phpThreads[i] = newPHPThread(i)
 		convertToInactiveThread(phpThreads[i])
 	}
 
+	if err := mainThread.start(); err != nil {
+		return err
+	}
+
 	// start the underlying C threads
 	ready := sync.WaitGroup{}
 	ready.Add(numThreads)
diff --git a/phpthread.go b/phpthread.go
index 067e7d2c2..f8ad9b62a 100644
--- a/phpthread.go
+++ b/phpthread.go
@@ -73,11 +73,10 @@ func (thread *phpThread) getActiveRequest() *http.Request {
 // Pin a string that is not null-terminated
 // PHP's zend_string may contain null-bytes
 func (thread *phpThread) pinString(s string) *C.char {
-	if s == "" {
+	sData := unsafe.StringData(s)
+	if sData == nil {
 		return nil
 	}
-
-	sData := unsafe.StringData(s)
 	thread.Pin(sData)
 
 	return (*C.char)(unsafe.Pointer(sData))