diff --git a/base/file.cpp b/base/file.cpp
index d6fe753..3834ed4 100644
--- a/base/file.cpp
+++ b/base/file.cpp
@@ -38,7 +38,6 @@
 #endif
 #if defined(_WIN32)
 #include <windows.h>
-#define O_CLOEXEC O_NOINHERIT
 #define O_NOFOLLOW 0
 #endif
 
diff --git a/base/include/android-base/file.h b/base/include/android-base/file.h
index 908690b..8f9bf80 100644
--- a/base/include/android-base/file.h
+++ b/base/include/android-base/file.h
@@ -21,11 +21,17 @@
 #include <string>
 
 #if !defined(_WIN32) && !defined(O_BINARY)
+/** Windows needs O_BINARY, but Unix never mangles line endings. */
 #define O_BINARY 0
 #endif
 
+#if defined(_WIN32) && !defined(O_CLOEXEC)
+/** Windows has O_CLOEXEC but calls it O_NOINHERIT for some reason. */
+#define O_CLOEXEC O_NOINHERIT
+#endif
+
 #if defined(__APPLE__)
-/* Mac OS has always had a 64-bit off_t, so it doesn't have off64_t. */
+/** Mac OS has always had a 64-bit off_t, so it doesn't have off64_t. */
 typedef off_t off64_t;
 #endif
 
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 925cac4..5101410 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -79,10 +79,6 @@
 using android::base::Trim;
 using android::base::unique_fd;
 
-#if defined(_WIN32)
-#define O_CLOEXEC O_NOINHERIT
-#endif
-
 static const char* serial = nullptr;
 
 static bool g_long_listing = false;