diff --git a/libraries/AP_FlashIface/AP_FlashIface_JEDEC.cpp b/libraries/AP_FlashIface/AP_FlashIface_JEDEC.cpp
index 47ed9198be..8aedfc6455 100644
--- a/libraries/AP_FlashIface/AP_FlashIface_JEDEC.cpp
+++ b/libraries/AP_FlashIface/AP_FlashIface_JEDEC.cpp
@@ -930,7 +930,7 @@ bool AP_FlashIface_JEDEC::start_xip_mode(void** addr)
             // Set QSPI module for XIP mode
             AP_HAL::QSPIDevice::CommandHeader cmd;
             cmd.cmd = _desc.fast_read_ins;  // generally 0xEB for 1-4-4 access
-            cmd.alt = 0xF0;                 // add M0-7 bits in alt to make up 32-bit address phase
+            cmd.alt = 0xF0;                 // add M0-7 bits in alt to make up 32-bit address phase, sec 8.2.11 W25Q64JV reference
             cmd.cfg = AP_HAL::QSPI::CFG_ADDR_SIZE_24 |
                       AP_HAL::QSPI::CFG_CMD_MODE_ONE_LINE |
                       AP_HAL::QSPI::CFG_ADDR_MODE_FOUR_LINES |