diff --git a/ble/att.h b/ble/att.h
index 2c69f57a7..97ed5357f 100644
--- a/ble/att.h
+++ b/ble/att.h
@@ -43,6 +43,9 @@
 extern "C" {
 #endif
 
+// Minimum/default MTU
+#define ATT_DEFAULT_MTU               23
+
 // MARK: Attribute PDU Opcodes 
 #define ATT_ERROR_RESPONSE              0x01