diff --git a/arch/arm/src/stm32/stm32_serial.c b/arch/arm/src/stm32/stm32_serial.c
index 077bb71641..b0edc1be14 100644
--- a/arch/arm/src/stm32/stm32_serial.c
+++ b/arch/arm/src/stm32/stm32_serial.c
@@ -2761,6 +2761,7 @@ void up_serialinit(void)
 #ifdef CONFIG_PM
   ret = pm_register(&g_serialcb);
   DEBUGASSERT(ret == OK);
+  UNUSED(ret);
 #endif
 
   /* Register the console */