diff --git a/src/flac/decode.c b/src/flac/decode.c
index 05d86f3..2173669 100644
--- a/src/flac/decode.c
+++ b/src/flac/decode.c
@@ -29,10 +29,14 @@
 #if defined _MSC_VER || defined __MINGW32__
 #include <sys/types.h> /* for off_t */
 #if _MSC_VER <= 1600 /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include <errno.h>
 #include <math.h> /* for floor() */
 #include <stdio.h> /* for FILE etc. */
diff --git a/src/flac/encode.c b/src/flac/encode.c
index dafa105..87ef2ef 100644
--- a/src/flac/encode.c
+++ b/src/flac/encode.c
@@ -29,10 +29,14 @@
 #if defined _MSC_VER || defined __MINGW32__
 #include <sys/types.h> /* for off_t */
 #if _MSC_VER <= 1600 /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include <errno.h>
 #include <limits.h> /* for LONG_MAX */
 #include <math.h> /* for floor() */
diff --git a/src/flac/foreign_metadata.c b/src/flac/foreign_metadata.c
index 7e273a5..d4fb7c2 100644
--- a/src/flac/foreign_metadata.c
+++ b/src/flac/foreign_metadata.c
@@ -23,10 +23,14 @@
 #if defined _MSC_VER || defined __MINGW32__
 #include <sys/types.h> /* for off_t */
 #if _MSC_VER <= 1600 /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include <stdio.h> /* for FILE etc. */
 #include <stdlib.h> /* for calloc() etc. */
 #include <string.h> /* for memcmp() etc. */
diff --git a/src/flac/iffscan.c b/src/flac/iffscan.c
index da74a5f..2cb9075 100644
--- a/src/flac/iffscan.c
+++ b/src/flac/iffscan.c
@@ -26,10 +26,14 @@
 #if defined _MSC_VER || defined __MINGW32__
 #include <sys/types.h> /* for off_t */
 #if _MSC_VER <= 1600 /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include "foreign_metadata.h"
 
 static FLAC__uint32 unpack32be_(const FLAC__byte *b)
diff --git a/src/libFLAC/metadata_iterators.c b/src/libFLAC/metadata_iterators.c
index ac6473e..9ef9882 100644
--- a/src/libFLAC/metadata_iterators.c
+++ b/src/libFLAC/metadata_iterators.c
@@ -47,9 +47,13 @@
 #include <io.h> /* for chmod() */
 #include <sys/types.h> /* for off_t */
 #if _MSC_VER <= 1600 || defined __BORLANDC__ /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
+#endif
 #else
 #include <sys/types.h> /* some flavors of BSD (like OS X) require this to get time_t */
 #include <utime.h> /* for utime() */
diff --git a/src/libFLAC/stream_decoder.c b/src/libFLAC/stream_decoder.c
index 72d9e43..0323d73 100644
--- a/src/libFLAC/stream_decoder.c
+++ b/src/libFLAC/stream_decoder.c
@@ -48,10 +48,14 @@
 #include <sys/types.h> /* for off_t */
 #if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__
 #if _MSC_VER <= 1600 || defined __BORLANDC__ /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include "FLAC/assert.h"
 #include "share/alloc.h"
 #include "protected/stream_decoder.h"
diff --git a/src/libFLAC/stream_encoder.c b/src/libFLAC/stream_encoder.c
index 8fb3209..0b6d8c2 100644
--- a/src/libFLAC/stream_encoder.c
+++ b/src/libFLAC/stream_encoder.c
@@ -48,10 +48,14 @@
 #include <sys/types.h> /* for off_t */
 #if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__
 #if _MSC_VER <= 1600 || defined __BORLANDC__ /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include "FLAC/assert.h"
 #include "FLAC/stream_decoder.h"
 #include "share/alloc.h"
diff --git a/src/test_libFLAC/decoders.c b/src/test_libFLAC/decoders.c
index e45e722..70127cf 100644
--- a/src/test_libFLAC/decoders.c
+++ b/src/test_libFLAC/decoders.c
@@ -26,10 +26,14 @@
 #include <string.h>
 #if defined _MSC_VER || defined __MINGW32__
 #if _MSC_VER <= 1600 /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
 #endif
+#endif
 #include "decoders.h"
 #include "FLAC/assert.h"
 #include "FLAC/stream_decoder.h"
diff --git a/src/test_libFLAC/metadata_manip.c b/src/test_libFLAC/metadata_manip.c
index 4214383..6644e79 100644
--- a/src/test_libFLAC/metadata_manip.c
+++ b/src/test_libFLAC/metadata_manip.c
@@ -27,9 +27,13 @@
 #include <sys/utime.h> /* for utime() */
 #include <io.h> /* for chmod() */
 #if _MSC_VER <= 1600 /* @@@ [2G limit] */
+#ifndef fseeko
 #define fseeko fseek
+#endif
+#ifndef ftello
 #define ftello ftell
 #endif
+#endif
 #else
 #include <sys/types.h> /* some flavors of BSD (like OS X) require this to get time_t */
 #include <utime.h> /* for utime() */