diff --git a/lib/stm32/f1/gpio.c b/lib/stm32/f1/gpio.c
index 4f7e663d..9ef60370 100644
--- a/lib/stm32/f1/gpio.c
+++ b/lib/stm32/f1/gpio.c
@@ -147,5 +147,8 @@ void gpio_port_config_lock(u32 gpioport, u16 gpios)
 	reg32 = GPIO_LCKR(gpioport);			/* Read LCKK. */
 	reg32 = GPIO_LCKR(gpioport);			/* Read LCKK again. */
 
+	/* Tell the compiler the variable is actually used. It will get optimized out anyways. */
+	reg32 = reg32; 
+
 	/* If (reg32 & GPIO_LCKK) is true, the lock is now active. */
 }
diff --git a/lib/stm32/f2/gpio.c b/lib/stm32/f2/gpio.c
index 7a381204..fc7a5b69 100644
--- a/lib/stm32/f2/gpio.c
+++ b/lib/stm32/f2/gpio.c
@@ -135,5 +135,8 @@ void gpio_port_config_lock(u32 gpioport, u16 gpios)
 	reg32 = GPIO_LCKR(gpioport);			/* Read LCKK. */
 	reg32 = GPIO_LCKR(gpioport);			/* Read LCKK again. */
 
+	/* Tell the compiler the variable is actually used. It will get optimized out anyways. */
+	reg32 = reg32; 
+
 	/* If (reg32 & GPIO_LCKK) is true, the lock is now active. */
 }
diff --git a/lib/stm32/f4/gpio.c b/lib/stm32/f4/gpio.c
index dea37208..e721f3f6 100644
--- a/lib/stm32/f4/gpio.c
+++ b/lib/stm32/f4/gpio.c
@@ -135,5 +135,8 @@ void gpio_port_config_lock(u32 gpioport, u16 gpios)
 	reg32 = GPIO_LCKR(gpioport);			/* Read LCKK. */
 	reg32 = GPIO_LCKR(gpioport);			/* Read LCKK again. */
 
+	/* Tell the compiler the variable is actually used. It will get optimized out anyways. */
+	reg32 = reg32; 
+
 	/* If (reg32 & GPIO_LCKK) is true, the lock is now active. */
 }
diff --git a/lib/stm32/nvic.c b/lib/stm32/nvic.c
index cd823e11..c9cf48bc 100644
--- a/lib/stm32/nvic.c
+++ b/lib/stm32/nvic.c
@@ -57,7 +57,7 @@ u8 nvic_get_irq_enabled(u8 irqn)
 
 void nvic_set_priority(u8 irqn, u8 priority)
 {
-	NVIC_IPR(irqn / 4) |= (priority << ((irqn % 4) * 8));
+	NVIC_IPR(irqn) = priority;
 }
 
 void nvic_generate_software_interrupt(u8 irqn)