diff --git a/drivers/pinctrl/pinctrl-st.c b/drivers/pinctrl/pinctrl-st.c
index 99da4cf91031..b926c744193b 100644
--- a/drivers/pinctrl/pinctrl-st.c
+++ b/drivers/pinctrl/pinctrl-st.c
@@ -1006,7 +1006,7 @@ static void st_pinconf_dbg_show(struct pinctrl_dev *pctldev,
 
 	function = st_pctl_get_pin_function(pc, offset);
 	if (function)
-		snprintf(f, 10, "Alt Fn %d", function);
+		snprintf(f, 10, "Alt Fn %u", function);
 	else
 		snprintf(f, 5, "GPIO");