diff --git a/tools/src/h5perf/pio_engine.c b/tools/src/h5perf/pio_engine.c
index 8b11f51fc68..7930d9645a0 100644
--- a/tools/src/h5perf/pio_engine.c
+++ b/tools/src/h5perf/pio_engine.c
@@ -72,12 +72,6 @@
     } while (0)
 
 /* POSIX I/O macros */
-#ifdef H5_HAVE_WIN32_API
-/* Can't link against the library, so this test will use the older, non-Unicode
- * _open() call on Windows.
- */
-#define HDopen(S, F, ...) _open(S, F | _O_BINARY, __VA_ARGS__)
-#endif /* H5_HAVE_WIN32_API */
 #define POSIXCREATE(fn)     HDopen(fn, O_CREAT | O_TRUNC | O_RDWR, 0600)
 #define POSIXOPEN(fn, F)    HDopen(fn, F, 0600)
 #define POSIXCLOSE(F)       HDclose(F)
diff --git a/tools/src/h5perf/sio_engine.c b/tools/src/h5perf/sio_engine.c
index 12305f54a76..0d2240fa69f 100644
--- a/tools/src/h5perf/sio_engine.c
+++ b/tools/src/h5perf/sio_engine.c
@@ -53,12 +53,6 @@
     } while (0)
 
 /* POSIX I/O macros */
-#ifdef H5_HAVE_WIN32_API
-/* Can't link against the library, so this test will use the older, non-Unicode
- * _open() call on Windows.
- */
-#define HDopen(S, F, ...) _open(S, F | _O_BINARY, __VA_ARGS__)
-#endif /* H5_HAVE_WIN32_API */
 #define POSIXCREATE(fn)     HDopen(fn, O_CREAT | O_TRUNC | O_RDWR, 0600)
 #define POSIXOPEN(fn, F)    HDopen(fn, F, 0600)
 #define POSIXCLOSE(F)       HDclose(F)