diff --git a/frankenphp.c b/frankenphp.c
index 60d2b8157..ac5007ba9 100644
--- a/frankenphp.c
+++ b/frankenphp.c
@@ -78,7 +78,7 @@ typedef struct frankenphp_server_context {
 } frankenphp_server_context;
 
 __thread frankenphp_server_context *local_ctx = NULL;
-__thread int thread_index;
+__thread uint32_t thread_index;
 
 static void frankenphp_free_request_context() {
   frankenphp_server_context *ctx = SG(server_context);
@@ -724,7 +724,7 @@ static void set_thread_name(char *thread_name) {
 static void *php_thread(void *arg) {
   char thread_name[16] = {0};
   snprintf(thread_name, 16, "php-%" PRIxPTR, (uintptr_t)arg);
-  thread_index = (int)(uintptr_t)arg;
+  thread_index = (uint32_t)(uintptr_t)arg;
   set_thread_name(thread_name);
 
 #ifdef ZTS
diff --git a/frankenphp.go b/frankenphp.go
index 0d17e4b85..f65c40f08 100644
--- a/frankenphp.go
+++ b/frankenphp.go
@@ -502,7 +502,7 @@ func ServeHTTP(responseWriter http.ResponseWriter, request *http.Request) error
 }
 
 //export go_handle_request
-func go_handle_request(threadIndex int) bool {
+func go_handle_request(threadIndex C.uint32_t) bool {
 	select {
 	case <-done:
 		return false
@@ -541,7 +541,7 @@ func maybeCloseContext(fc *FrankenPHPContext) {
 }
 
 //export go_ub_write
-func go_ub_write(threadIndex int, cBuf *C.char, length C.int) (C.size_t, C.bool) {
+func go_ub_write(threadIndex C.uint32_t, cBuf *C.char, length C.int) (C.size_t, C.bool) {
 	r := getPHPThread(threadIndex).getActiveRequest()
 	fc, _ := FromContext(r.Context())
 
@@ -580,7 +580,7 @@ var headerKeyCache = func() otter.Cache[string, string] {
 }()
 
 //export go_register_variables
-func go_register_variables(threadIndex int, trackVarsArray *C.zval) {
+func go_register_variables(threadIndex C.uint32_t, trackVarsArray *C.zval) {
 	thread := getPHPThread(threadIndex)
 	r := thread.getActiveRequest()
 	fc := r.Context().Value(contextKey).(*FrankenPHPContext)
@@ -649,7 +649,7 @@ func go_register_variables(threadIndex int, trackVarsArray *C.zval) {
 }
 
 //export go_apache_request_headers
-func go_apache_request_headers(threadIndex int, hasActiveRequest bool) (*C.go_string, C.size_t) {
+func go_apache_request_headers(threadIndex C.uint32_t, hasActiveRequest bool) (*C.go_string, C.size_t) {
 	thread := getPHPThread(threadIndex)
 
 	if !hasActiveRequest {
@@ -691,7 +691,7 @@ func go_apache_request_headers(threadIndex int, hasActiveRequest bool) (*C.go_st
 }
 
 //export go_apache_request_cleanup
-func go_apache_request_cleanup(threadIndex int) {
+func go_apache_request_cleanup(threadIndex C.uint32_t) {
 	getPHPThread(threadIndex).pinner.Unpin()
 }
 
@@ -709,7 +709,7 @@ func addHeader(fc *FrankenPHPContext, cString *C.char, length C.int) {
 }
 
 //export go_write_headers
-func go_write_headers(threadIndex int, status C.int, headers *C.zend_llist) {
+func go_write_headers(threadIndex C.uint32_t, status C.int, headers *C.zend_llist) {
 	r := getPHPThread(threadIndex).getActiveRequest()
 	fc := r.Context().Value(contextKey).(*FrankenPHPContext)
 
@@ -737,7 +737,7 @@ func go_write_headers(threadIndex int, status C.int, headers *C.zend_llist) {
 }
 
 //export go_sapi_flush
-func go_sapi_flush(threadIndex int) bool {
+func go_sapi_flush(threadIndex C.uint32_t) bool {
 	r := getPHPThread(threadIndex).getActiveRequest()
 	fc := r.Context().Value(contextKey).(*FrankenPHPContext)
 
@@ -755,7 +755,7 @@ func go_sapi_flush(threadIndex int) bool {
 }
 
 //export go_read_post
-func go_read_post(threadIndex int, cBuf *C.char, countBytes C.size_t) (readBytes C.size_t) {
+func go_read_post(threadIndex C.uint32_t, cBuf *C.char, countBytes C.size_t) (readBytes C.size_t) {
 	r := getPHPThread(threadIndex).getActiveRequest()
 
 	p := unsafe.Slice((*byte)(unsafe.Pointer(cBuf)), countBytes)
@@ -770,7 +770,7 @@ func go_read_post(threadIndex int, cBuf *C.char, countBytes C.size_t) (readBytes
 }
 
 //export go_read_cookies
-func go_read_cookies(threadIndex int) *C.char {
+func go_read_cookies(threadIndex C.uint32_t) *C.char {
 	r := getPHPThread(threadIndex).getActiveRequest()
 
 	cookies := r.Cookies()
diff --git a/php_thread.go b/php_thread.go
index aaa072fb3..5ff759a29 100644
--- a/php_thread.go
+++ b/php_thread.go
@@ -1,5 +1,7 @@
 package frankenphp
 
+// #include <stdint.h>
+import "C"
 import (
 	"net/http"
 	"runtime"
@@ -22,8 +24,8 @@ func initializePHPThreads(numThreads int) {
 	}
 }
 
-func getPHPThread(threadIndex int) *phpThread {
-	return phpThreads[threadIndex]
+func getPHPThread(threadIndex C.uint32_t) *phpThread {
+	return phpThreads[int(threadIndex)]
 }
 
 func (thread *phpThread) setMainRequest(request *http.Request) {
diff --git a/php_thread_test.go b/php_thread_test.go
index a1497d723..3d8d1a767 100644
--- a/php_thread_test.go
+++ b/php_thread_test.go
@@ -24,6 +24,7 @@ func TestMainRequestIsActiveRequest(t *testing.T) {
 	thread.setMainRequest(mainRequest)
 
 	assert.Equal(t, mainRequest, thread.getActiveRequest())
+	assert.Equal(t, mainRequest, thread.getMainRequest())
 }
 
 func TestWorkerRequestIsActiveRequest(t *testing.T) {
diff --git a/worker.go b/worker.go
index 40669000d..7487cba79 100644
--- a/worker.go
+++ b/worker.go
@@ -239,7 +239,7 @@ func assignThreadToWorker(thread *phpThread) {
 }
 
 //export go_frankenphp_worker_handle_request_start
-func go_frankenphp_worker_handle_request_start(threadIndex int) C.bool {
+func go_frankenphp_worker_handle_request_start(threadIndex C.uint32_t) C.bool {
 	thread := getPHPThread(threadIndex)
 
 	// we assign a worker to the thread if it doesn't have one already
@@ -282,7 +282,7 @@ func go_frankenphp_worker_handle_request_start(threadIndex int) C.bool {
 }
 
 //export go_frankenphp_finish_request
-func go_frankenphp_finish_request(threadIndex int, isWorkerRequest bool) {
+func go_frankenphp_finish_request(threadIndex C.uint32_t, isWorkerRequest bool) {
 	thread := getPHPThread(threadIndex)
 	r := thread.getActiveRequest()
 	fc := r.Context().Value(contextKey).(*FrankenPHPContext)