diff --git a/subsys/modem/backends/modem_backend_tty.c b/subsys/modem/backends/modem_backend_tty.c
index e511150ae9d216..b9a1c8b7c88a40 100644
--- a/subsys/modem/backends/modem_backend_tty.c
+++ b/subsys/modem/backends/modem_backend_tty.c
@@ -103,7 +103,7 @@ static int modem_backend_tty_close(void *data)
 	return 0;
 }
 
-struct modem_pipe_api modem_backend_tty_api = {
+static const struct modem_pipe_api modem_backend_tty_api = {
 	.open = modem_backend_tty_open,
 	.transmit = modem_backend_tty_transmit,
 	.receive = modem_backend_tty_receive,
diff --git a/subsys/modem/backends/modem_backend_uart_async.c b/subsys/modem/backends/modem_backend_uart_async.c
index 184f83a8e461d1..1b18420f7ed2a4 100644
--- a/subsys/modem/backends/modem_backend_uart_async.c
+++ b/subsys/modem/backends/modem_backend_uart_async.c
@@ -269,7 +269,7 @@ static int modem_backend_uart_async_close(void *data)
 	return 0;
 }
 
-struct modem_pipe_api modem_backend_uart_async_api = {
+static const struct modem_pipe_api modem_backend_uart_async_api = {
 	.open = modem_backend_uart_async_open,
 	.transmit = modem_backend_uart_async_transmit,
 	.receive = modem_backend_uart_async_receive,
diff --git a/subsys/modem/backends/modem_backend_uart_isr.c b/subsys/modem/backends/modem_backend_uart_isr.c
index ea8d99d6032681..a9266cc86657b9 100644
--- a/subsys/modem/backends/modem_backend_uart_isr.c
+++ b/subsys/modem/backends/modem_backend_uart_isr.c
@@ -233,7 +233,7 @@ static int modem_backend_uart_isr_close(void *data)
 	return 0;
 }
 
-struct modem_pipe_api modem_backend_uart_isr_api = {
+static const struct modem_pipe_api modem_backend_uart_isr_api = {
 	.open = modem_backend_uart_isr_open,
 	.transmit = modem_backend_uart_isr_transmit,
 	.receive = modem_backend_uart_isr_receive,
diff --git a/subsys/modem/modem_cmux.c b/subsys/modem/modem_cmux.c
index 1f425ae4834424..583090700e505e 100644
--- a/subsys/modem/modem_cmux.c
+++ b/subsys/modem/modem_cmux.c
@@ -740,7 +740,7 @@ static void modem_cmux_process_received_byte(struct modem_cmux *cmux, uint8_t by
 
 	case MODEM_CMUX_RECEIVE_STATE_RESYNC:
 		/*
-		 * Allow any number of consequtive flags (0xF9).
+		 * Allow any number of consecutive flags (0xF9).
 		 * 0xF9 could also be a valid address field for DLCI 62.
 		 */
 		if (byte == 0xF9) {
@@ -992,7 +992,7 @@ static void modem_cmux_connect_handler(struct k_work *item)
 
 	cmux->state = MODEM_CMUX_STATE_CONNECTING;
 
-	struct modem_cmux_frame frame = {
+	static const struct modem_cmux_frame frame = {
 		.dlci_address = 0,
 		.cr = true,
 		.pf = true,
@@ -1154,7 +1154,7 @@ static int modem_cmux_dlci_pipe_api_close(void *data)
 	return ret;
 }
 
-struct modem_pipe_api modem_cmux_dlci_pipe_api = {
+static const struct modem_pipe_api modem_cmux_dlci_pipe_api = {
 	.open = modem_cmux_dlci_pipe_api_open,
 	.transmit = modem_cmux_dlci_pipe_api_transmit,
 	.receive = modem_cmux_dlci_pipe_api_receive,