diff --git a/fastboot/Android.bp b/fastboot/Android.bp
index 3c4269b7c..0ca8ba858 100644
--- a/fastboot/Android.bp
+++ b/fastboot/Android.bp
@@ -206,6 +206,7 @@ cc_defaults {
         "-Wextra",
         "-Werror",
         "-Wunreachable-code",
+        "-DANDROID_BASE_UNIQUE_FD_DISABLE_IMPLICIT_CONVERSION",
     ],
 
     target: {
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 402c5c5f7..783cd1974 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -230,9 +230,9 @@ static void InfoMessage(const std::string& info) {
     fprintf(stderr, "(bootloader) %s\n", info.c_str());
 }
 
-static int64_t get_file_size(int fd) {
+static int64_t get_file_size(borrowed_fd fd) {
     struct stat sb;
-    if (fstat(fd, &sb) == -1) {
+    if (fstat(fd.get(), &sb) == -1) {
         die("could not get file size");
     }
     return sb.st_size;
@@ -657,12 +657,12 @@ static unique_fd unzip_to_file(ZipArchiveHandle zip, const char* entry_name) {
     fprintf(stderr, "extracting %s (%" PRIu64 " MB) to disk...", entry_name,
             zip_entry.uncompressed_length / 1024 / 1024);
     double start = now();
-    int error = ExtractEntryToFile(zip, &zip_entry, fd);
+    int error = ExtractEntryToFile(zip, &zip_entry, fd.get());
     if (error != 0) {
         die("\nfailed to extract '%s': %s", entry_name, ErrorCodeString(error));
     }
 
-    if (lseek(fd, 0, SEEK_SET) != 0) {
+    if (lseek(fd.get(), 0, SEEK_SET) != 0) {
         die("\nlseek on extracted file '%s' failed: %s", entry_name, strerror(errno));
     }
 
@@ -902,14 +902,14 @@ static bool load_buf_fd(unique_fd fd, struct fastboot_buffer* buf) {
         return false;
     }
 
-    if (sparse_file* s = sparse_file_import(fd, false, false)) {
+    if (sparse_file* s = sparse_file_import(fd.get(), false, false)) {
         buf->image_size = sparse_file_len(s, false, false);
         sparse_file_destroy(s);
     } else {
         buf->image_size = sz;
     }
 
-    lseek(fd, 0, SEEK_SET);
+    lseek(fd.get(), 0, SEEK_SET);
     int64_t limit = get_sparse_limit(sz);
     buf->fd = std::move(fd);
     if (limit) {
@@ -936,7 +936,7 @@ static bool load_buf(const char* fname, struct fastboot_buffer* buf) {
     }
 
     struct stat s;
-    if (fstat(fd, &s)) {
+    if (fstat(fd.get(), &s)) {
         return false;
     }
     if (!S_ISREG(s.st_mode)) {
@@ -995,7 +995,7 @@ static void rewrite_vbmeta_buffer(struct fastboot_buffer* buf, bool vbmeta_in_bo
         die("Failed writing to modified vbmeta");
     }
     buf->fd = std::move(fd);
-    lseek(buf->fd, 0, SEEK_SET);
+    lseek(buf->fd.get(), 0, SEEK_SET);
 }
 
 static bool has_vbmeta_partition() {
@@ -1057,13 +1057,13 @@ static void copy_boot_avb_footer(const std::string& partition, struct fastboot_b
     if (!android::base::WriteStringToFd(data, fd)) {
         die("Failed writing to modified boot");
     }
-    lseek(fd, partition_size - AVB_FOOTER_SIZE, SEEK_SET);
+    lseek(fd.get(), partition_size - AVB_FOOTER_SIZE, SEEK_SET);
     if (!android::base::WriteStringToFd(data.substr(footer_offset), fd)) {
         die("Failed copying AVB footer in boot");
     }
     buf->fd = std::move(fd);
     buf->sz = partition_size;
-    lseek(buf->fd, 0, SEEK_SET);
+    lseek(buf->fd.get(), 0, SEEK_SET);
 }
 
 static void flash_buf(const std::string& partition, struct fastboot_buffer *buf)
@@ -1538,7 +1538,7 @@ void FlashAllTool::FlashImage(const Image& image, const std::string& slot, fastb
 }
 
 void FlashAllTool::UpdateSuperPartition() {
-    int fd = source_.OpenFile("super_empty.img");
+    unique_fd fd = source_.OpenFile("super_empty.img");
     if (fd < 0) {
         return;
     }
@@ -2197,7 +2197,7 @@ int FastBootTool::Main(int argc, char* argv[]) {
             if (!load_buf(filename.c_str(), &buf) || buf.type != FB_BUFFER_FD) {
                 die("cannot load '%s'", filename.c_str());
             }
-            fb->Download(filename, buf.fd, buf.sz);
+            fb->Download(filename, buf.fd.get(), buf.sz);
         } else if (command == "get_staged") {
             std::string filename = next_arg(&args);
             fb->Upload(filename);
diff --git a/fastboot/fastboot_driver.cpp b/fastboot/fastboot_driver.cpp
index 14ee78555..99a48734c 100644
--- a/fastboot/fastboot_driver.cpp
+++ b/fastboot/fastboot_driver.cpp
@@ -144,7 +144,8 @@ RetCode FastBootDriver::FlashPartition(const std::string& partition,
     return Flash(partition);
 }
 
-RetCode FastBootDriver::FlashPartition(const std::string& partition, int fd, uint32_t size) {
+RetCode FastBootDriver::FlashPartition(const std::string& partition, android::base::borrowed_fd fd,
+                                       uint32_t size) {
     RetCode ret;
     if ((ret = Download(partition, fd, size))) {
         return ret;
@@ -182,15 +183,16 @@ RetCode FastBootDriver::Partitions(std::vector<std::tuple<std::string, uint64_t>
     return SUCCESS;
 }
 
-RetCode FastBootDriver::Download(const std::string& name, int fd, size_t size,
-                                 std::string* response, std::vector<std::string>* info) {
+RetCode FastBootDriver::Download(const std::string& name, android::base::borrowed_fd fd,
+                                 size_t size, std::string* response,
+                                 std::vector<std::string>* info) {
     prolog_(StringPrintf("Sending '%s' (%zu KB)", name.c_str(), size / 1024));
     auto result = Download(fd, size, response, info);
     epilog_(result);
     return result;
 }
 
-RetCode FastBootDriver::Download(int fd, size_t size, std::string* response,
+RetCode FastBootDriver::Download(android::base::borrowed_fd fd, size_t size, std::string* response,
                                  std::vector<std::string>* info) {
     RetCode ret;
 
@@ -521,7 +523,7 @@ std::string FastBootDriver::ErrnoStr(const std::string& msg) {
 }
 
 /******************************* PRIVATE **************************************/
-RetCode FastBootDriver::SendBuffer(int fd, size_t size) {
+RetCode FastBootDriver::SendBuffer(android::base::borrowed_fd fd, size_t size) {
     static constexpr uint32_t MAX_MAP_SIZE = 512 * 1024 * 1024;
     off64_t offset = 0;
     uint32_t remaining = size;
diff --git a/fastboot/fastboot_driver.h b/fastboot/fastboot_driver.h
index f1c094f28..bccd6685f 100644
--- a/fastboot/fastboot_driver.h
+++ b/fastboot/fastboot_driver.h
@@ -77,9 +77,9 @@ class FastBootDriver {
     RetCode Continue(std::string* response = nullptr, std::vector<std::string>* info = nullptr);
     RetCode CreatePartition(const std::string& partition, const std::string& size);
     RetCode DeletePartition(const std::string& partition);
-    RetCode Download(const std::string& name, int fd, size_t size, std::string* response = nullptr,
-                     std::vector<std::string>* info = nullptr);
-    RetCode Download(int fd, size_t size, std::string* response = nullptr,
+    RetCode Download(const std::string& name, android::base::borrowed_fd fd, size_t size,
+                     std::string* response = nullptr, std::vector<std::string>* info = nullptr);
+    RetCode Download(android::base::borrowed_fd fd, size_t size, std::string* response = nullptr,
                      std::vector<std::string>* info = nullptr);
     RetCode Download(const std::string& name, const std::vector<char>& buf,
                      std::string* response = nullptr, std::vector<std::string>* info = nullptr);
@@ -113,7 +113,8 @@ class FastBootDriver {
 
     /* HIGHER LEVEL COMMANDS -- Composed of the commands above */
     RetCode FlashPartition(const std::string& partition, const std::vector<char>& data);
-    RetCode FlashPartition(const std::string& partition, int fd, uint32_t sz);
+    RetCode FlashPartition(const std::string& partition, android::base::borrowed_fd fd,
+                           uint32_t sz);
     RetCode FlashPartition(const std::string& partition, sparse_file* s, uint32_t sz,
                            size_t current, size_t total);
 
@@ -149,7 +150,7 @@ class FastBootDriver {
     Transport* transport_;
 
   private:
-    RetCode SendBuffer(int fd, size_t size);
+    RetCode SendBuffer(android::base::borrowed_fd fd, size_t size);
     RetCode SendBuffer(const std::vector<char>& buf);
     RetCode SendBuffer(const void* buf, size_t size);