diff --git a/libmaxsi/c/decl/FILE.h b/libmaxsi/c/decl/FILE.h
index 66c5911f..29c9b6c5 100644
--- a/libmaxsi/c/decl/FILE.h
+++ b/libmaxsi/c/decl/FILE.h
@@ -15,7 +15,7 @@ typedef struct _FILE
 	void* user;
 	size_t (*read_func)(void* ptr, size_t size, size_t nmemb, void* user);
 	size_t (*write_func)(const void* ptr, size_t size, size_t nmemb, void* user);
-	int (*seek_func)(void* user, long offset, int whence);
+	int (*seek_func)(void* user, off_t offset, int whence);
 	long (*tell_func)(void* user);
 	void (*clearerr_func)(void* user);
 	int (*eof_func)(void* user);
diff --git a/libmaxsi/c/fdio.c b/libmaxsi/c/fdio.c
index 701a7aed..947e4a03 100644
--- a/libmaxsi/c/fdio.c
+++ b/libmaxsi/c/fdio.c
@@ -74,16 +74,16 @@ static size_t fdio_write(const void* ptr, size_t size, size_t nmemb, void* user)
 	return sofar;
 }
 
-static int fdio_seek(void* user, long offset, int whence)
+static int fdio_seek(void* user, off_t offset, int whence)
 {
 	fdio_t* fdio = (fdio_t*) user;
 	return (int) lseek(fdio->fd, offset, whence);
 }
 
-static long fdio_tell(void* user)
+static off_t fdio_tell(void* user)
 {
 	fdio_t* fdio = (fdio_t*) user;
-	return (int) lseek(fdio->fd, 0, SEEK_CUR);
+	return lseek(fdio->fd, 0, SEEK_CUR);
 }
 
 static void fdio_clearerr(void* user)
diff --git a/libmaxsi/c/file.c b/libmaxsi/c/file.c
index b7695be3..57af98a4 100644
--- a/libmaxsi/c/file.c
+++ b/libmaxsi/c/file.c
@@ -91,11 +91,16 @@ size_t fwrite(const void* ptr, size_t size, size_t nmemb, FILE* fp)
 	return sofar;
 }
 
-int fseek(FILE* fp, long offset, int whence)
+int fseeko(FILE* fp, off_t offset, int whence)
 {
 	return (fp->seek_func) ? fp->seek_func(fp->user, offset, whence) : 0;
 }
 
+int fseek(FILE* fp, long offset, int whence)
+{
+	return fseeko(fp, offset, whence);
+}
+
 void clearerr(FILE* fp)
 {
 	if ( fp->clearerr_func ) { fp->clearerr_func(fp->user); }
@@ -119,12 +124,17 @@ void rewind(FILE* fp)
 	clearerr(fp);
 }
 
-long ftell(FILE* fp)
+off_t ftello(FILE* fp)
 {
 	if ( !fp->tell_func ) { errno = EBADF; return -1; }
 	return fp->tell_func(fp->user);
 }
 
+long ftell(FILE* fp)
+{
+	return (long) ftello(fp);
+}
+
 int fflush(FILE* fp)
 {
 	if ( !fp )