diff --git a/hw/arm/strongarm.c b/hw/arm/strongarm.c
index ec2627374d..644a9c45b4 100644
--- a/hw/arm/strongarm.c
+++ b/hw/arm/strongarm.c
@@ -587,12 +587,12 @@ static void strongarm_gpio_write(void *opaque, hwaddr offset,
 
     switch (offset) {
     case GPDR:        /* GPIO Pin-Direction registers */
-        s->dir = value;
+        s->dir = value & 0x0fffffff;
         strongarm_gpio_handler_update(s);
         break;
 
     case GPSR:        /* GPIO Pin-Output Set registers */
-        s->olevel |= value;
+        s->olevel |= value & 0x0fffffff;
         strongarm_gpio_handler_update(s);
         break;