diff --git a/drivers/modem/Kconfig.cellular b/drivers/modem/Kconfig.cellular
index 60528faefdf25..b4be5b69d808e 100644
--- a/drivers/modem/Kconfig.cellular
+++ b/drivers/modem/Kconfig.cellular
@@ -21,6 +21,13 @@ config MODEM_CELLULAR
 		    DT_HAS_QUECTEL_EG25_G_ENABLED || DT_HAS_NORDIC_NRF91_SLM_ENABLED || \
 		    DT_HAS_SQN_GM02S_ENABLED || DT_HAS_U_BLOX_LARA_R6_ENABLED || \
 		    DT_HAS_QUECTEL_EG800Q_ENABLED)
+	select MODEM_CMUX_DEFAULT_MTU_127 if \
+		(DT_HAS_QUECTEL_BG95_ENABLED || DT_HAS_QUECTEL_EG25_G_ENABLED || \
+		 DT_HAS_SIMCOM_SIM7080_ENABLED || DT_HAS_U_BLOX_SARA_R4_ENABLED || \
+		 DT_HAS_U_BLOX_SARA_R5_ENABLED || DT_HAS_SWIR_HL7800_ENABLED || \
+		 DT_HAS_TELIT_ME910G1_ENABLED || DT_HAS_TELIT_ME310G1_ENABLED || \
+		 DT_HAS_SQN_GM02S_ENABLED || DT_HAS_QUECTEL_EG800Q_ENABLED || \
+		 DT_HAS_SIMCOM_A76XX_ENABLED)
 	help
 	  This driver uses the generic 3gpp AT commands, along
 	  with the standard protocols CMUX and PPP, to configure
diff --git a/subsys/modem/Kconfig b/subsys/modem/Kconfig
index dcbb5bf99a044..c4f4c0cd8982c 100644
--- a/subsys/modem/Kconfig
+++ b/subsys/modem/Kconfig
@@ -31,15 +31,8 @@ if MODEM_CMUX
 
 config MODEM_CMUX_DEFAULT_MTU_127
 	bool
-	default y if (DT_HAS_QUECTEL_BG95_ENABLED || DT_HAS_QUECTEL_EG25_G_ENABLED || \
-		      DT_HAS_SIMCOM_SIM7080_ENABLED || DT_HAS_U_BLOX_SARA_R4_ENABLED || \
-		      DT_HAS_U_BLOX_SARA_R5_ENABLED || DT_HAS_SWIR_HL7800_ENABLED || \
-		      DT_HAS_TELIT_ME910G1_ENABLED || DT_HAS_TELIT_ME310G1_ENABLED || \
-		      DT_HAS_SQN_GM02S_ENABLED || DT_HAS_QUECTEL_EG800Q_ENABLED || \
-		      DT_HAS_SIMCOM_A76XX_ENABLED)
 	help
-	  Use the default MTU size of 127 bytes for the CMUX module on certain modems.
-	  This must match the AT+CMUX commands in the modem_cellular driver.
+	  Hint that the default MODEM_CMUX_MTU size should be 127 bytes.
 
 config MODEM_CMUX_MTU
 	int "CMUX MTU size in bytes"