diff --git a/arch/arm/src/sam34/chip/sam4s_pio.h b/arch/arm/src/sam34/chip/sam4s_pio.h
index 93111dddbbc..b208b77562b 100644
--- a/arch/arm/src/sam34/chip/sam4s_pio.h
+++ b/arch/arm/src/sam34/chip/sam4s_pio.h
@@ -359,6 +359,7 @@
 #define PIO_WPMR_WPEN              (1 << 0)  /* Bit 0:  Write Protect Enable */
 #define PIO_WPMR_WPKEY_SHIFT       (8)       /* Bits 8-31: Write Protect KEY */
 #define PIO_WPMR_WPKEY_MASK        (0xffffff << PIO_WPMR_WPKEY_SHIFT)
+#  define PIO_WPMR_WPKEY           (0x50494f << PIO_WPMR_WPKEY_SHIFT)
 
 /* PIO Write Protect Status Register */