diff --git a/ibm_db2.stub.php b/ibm_db2.stub.php
index 693548d..71d3012 100644
--- a/ibm_db2.stub.php
+++ b/ibm_db2.stub.php
@@ -337,4 +337,4 @@ function db2_getoption($resource, string $option): string|false {}
 /**
  * @param resource $resource
  */
-function db2_last_insert_id($resource): string {}
+function db2_last_insert_id($resource): ?string {}
diff --git a/ibm_db2_arginfo.h b/ibm_db2_arginfo.h
index 0d45be1..32aed10 100644
--- a/ibm_db2_arginfo.h
+++ b/ibm_db2_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: e952caf6e14487291104ab1f1fdd7f268cc8a6bc */
+ * Stub hash: 3cbc4e7e9448199bff07235c7abe69943e4d239d */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_db2_connect, 0, 0, 3)
 	ZEND_ARG_TYPE_INFO(0, database, IS_STRING, 0)
@@ -243,7 +243,7 @@ ZEND_END_ARG_INFO()
 
 #define arginfo_db2_getoption arginfo_db2_get_option
 
-ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_db2_last_insert_id, 0, 1, IS_STRING, 0)
+ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_db2_last_insert_id, 0, 1, IS_STRING, 1)
 	ZEND_ARG_INFO(0, resource)
 ZEND_END_ARG_INFO()
 
diff --git a/ibm_db2_legacy_arginfo.h b/ibm_db2_legacy_arginfo.h
index 4a02a9e..fb8256e 100644
--- a/ibm_db2_legacy_arginfo.h
+++ b/ibm_db2_legacy_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: e952caf6e14487291104ab1f1fdd7f268cc8a6bc */
+ * Stub hash: 3cbc4e7e9448199bff07235c7abe69943e4d239d */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_db2_connect, 0, 0, 3)
 	ZEND_ARG_INFO(0, database)
diff --git a/tests/test_last_insert_id.phpt b/tests/test_last_insert_id.phpt
index d9b3a3d..ac5935c 100644
--- a/tests/test_last_insert_id.phpt
+++ b/tests/test_last_insert_id.phpt
@@ -22,7 +22,7 @@ if ($conn) {
 
 	/* Checking when no insert has been executed. */	
 	$ret =  db2_last_insert_id($conn);
-	if($ret) {
+	if (null !== $ret) {
 		echo "Last Insert ID is : " . $ret . "\n";
 	} else {
 		echo "No Last insert ID.\n";
@@ -31,7 +31,7 @@ if ($conn) {
 	/* Inserting many rows from VALUES clause */
 	$stmt = db2_exec($conn, $insertMany);
 	$ret =  db2_last_insert_id($conn);
-	if($ret) {
+	if (null !== $ret) {
 		echo "Last Insert ID is : " . $ret . "\n";
 	} else {
 		echo "No Last insert ID.\n";
@@ -40,7 +40,7 @@ if ($conn) {
 	/* Checking for single row inserted. */
 	$stmt = db2_exec($conn, $insertTable);
 	$ret =  db2_last_insert_id($conn);
-	if($ret) {
+	if (null !== $ret) {
 		echo "Last Insert ID is : " . $ret . "\n";
 	} else {
 		echo "No Last insert ID.\n";
@@ -50,7 +50,7 @@ if ($conn) {
 	for ($i = 0;$i < 5;$i++) {
 		$stmt = db2_exec($conn, $insertTable);
 		$ret =  db2_last_insert_id($conn);
-		if($ret) {
+		if (null !== $ret) {
 			echo "Last Insert ID is : " . $ret . "\n";
 		} else {
 			echo "No Last insert ID.\n";
@@ -78,7 +78,7 @@ if ($conn) {
 
 	$stmt = db2_exec($conn, $insertTable);
 	$ret =  db2_last_insert_id($conn);
-	if($ret) {
+	if (null !== $ret) {
 		echo "Last Insert ID is : " . $ret . "\n";
 	} else {
 		echo "No Last insert ID.\n";