diff --git a/Tools/AP_Bootloader/bl_protocol.cpp b/Tools/AP_Bootloader/bl_protocol.cpp
index 5bc0df7b28..9b505664d6 100644
--- a/Tools/AP_Bootloader/bl_protocol.cpp
+++ b/Tools/AP_Bootloader/bl_protocol.cpp
@@ -422,23 +422,23 @@ static void test_flash()
             }
             uint32_t num_writes = flash_func_sector_size(page) / sizeof(v);
             uprintf("page %u size %u addr=0x%08x v=0x%08x\n",
-                    page, flash_func_sector_size(page), addr, v[0]); delay(10);
+                    unsigned(page), unsigned(flash_func_sector_size(page)), unsigned(addr), unsigned(v[0])); delay(10);
             if (init_done) {
                 for (uint32_t j=0; j<flash_func_sector_size(page)/4; j++) {
                     uint32_t v1 = (page<<16) + (loop-1);
                     uint32_t v2 = flash_func_read_word(addr+j*4);
                     if (v2 != v1) {
-                        uprintf("read error at 0x%08x v=0x%08x v2=0x%08x\n", addr+j*4, v1, v2);
+                        uprintf("read error at 0x%08x v=0x%08x v2=0x%08x\n", unsigned(addr+j*4), unsigned(v1), unsigned(v2));
                         break;
                     }
                 }
             }
             if (!flash_func_erase_sector(page)) {
-                uprintf("erase of %u failed\n", page);
+                uprintf("erase of %u failed\n", unsigned(page));
             }
             for (uint32_t j=0; j<num_writes; j++) {
                 if (!flash_func_write_words(addr+j*sizeof(v), v, ARRAY_SIZE(v))) {
-                    uprintf("write failed at 0x%08x\n", addr+j*sizeof(v));
+                    uprintf("write failed at 0x%08x\n", unsigned(addr+j*sizeof(v)));
                     break;
                 }
             }