diff --git a/drivers/modem/gsm_ppp.c b/drivers/modem/gsm_ppp.c
index 5ac4a3fb9fe..7093e4678e6 100644
--- a/drivers/modem/gsm_ppp.c
+++ b/drivers/modem/gsm_ppp.c
@@ -30,6 +30,10 @@ LOG_MODULE_REGISTER(modem_gsm, CONFIG_MODEM_LOG_LEVEL);
 #define GSM_CMD_READ_BUF                128
 #define GSM_CMD_AT_TIMEOUT              K_SECONDS(2)
 #define GSM_CMD_SETUP_TIMEOUT           K_SECONDS(6)
+/* GSM_CMD_LOCK_TIMEOUT should be longer than GSM_CMD_AT_TIMEOUT & GSM_CMD_SETUP_TIMEOUT,
+ * otherwise the gsm_ppp_stop might fail to lock tx.
+ */
+#define GSM_CMD_LOCK_TIMEOUT            K_SECONDS(10)
 #define GSM_RX_STACK_SIZE               CONFIG_MODEM_GSM_RX_STACK_SIZE
 #define GSM_WORKQ_STACK_SIZE            CONFIG_MODEM_GSM_WORKQ_STACK_SIZE
 #define GSM_RECV_MAX_BUF                30
@@ -1054,8 +1058,7 @@ void gsm_ppp_stop(const struct device *dev)
 		}
 	}
 
-	if (modem_cmd_handler_tx_lock(&gsm->context.cmd_handler,
-				      K_SECONDS(10))) {
+	if (modem_cmd_handler_tx_lock(&gsm->context.cmd_handler, GSM_CMD_LOCK_TIMEOUT)) {
 		LOG_WRN("Failed locking modem cmds!");
 	}