diff --git a/include/bluetooth/addr.h b/include/bluetooth/addr.h
index 37e1bf268a0..bd6669baa08 100644
--- a/include/bluetooth/addr.h
+++ b/include/bluetooth/addr.h
@@ -30,10 +30,17 @@ extern "C" {
 #define BT_ADDR_LE_PUBLIC_ID    0x02
 #define BT_ADDR_LE_RANDOM_ID    0x03
 
+/** Length in bytes of a standard Bluetooth address */
+#define BT_ADDR_SIZE 6
+
 /** Bluetooth Device Address */
 typedef struct {
-	uint8_t  val[6];
+	uint8_t  val[BT_ADDR_SIZE];
 } bt_addr_t;
+/**/
+
+/** Length in bytes of an LE Bluetooth address. Not packed, so no sizeof() */
+#define BT_ADDR_LE_SIZE 7
 
 /** Bluetooth LE Device Address */
 typedef struct {
diff --git a/subsys/bluetooth/common/dummy.c b/subsys/bluetooth/common/dummy.c
index 7a2bdb81a92..dd3d45ff7c8 100644
--- a/subsys/bluetooth/common/dummy.c
+++ b/subsys/bluetooth/common/dummy.c
@@ -10,6 +10,17 @@
  */
 
 #include <zephyr.h>
+#include <bluetooth/bluetooth.h>
+
+/*
+ * The unpacked structs below are used inside __packed structures that reflect
+ * what goes on the wire. While alignment is not a problem for those, since all
+ * their members are bytes or byte arrays, the size is. They must not be padded
+ * by the compiler, otherwise the on-wire packet will not map the packed
+ * structure correctly.
+ */
+BUILD_ASSERT(sizeof(bt_addr_t) == BT_ADDR_SIZE);
+BUILD_ASSERT(sizeof(bt_addr_le_t) == BT_ADDR_LE_SIZE);
 
 #if defined(CONFIG_BT_HCI_HOST)
 /* The Bluetooth subsystem requires the Tx thread to execute at higher priority