diff --git a/libsrc/posixio.c b/libsrc/posixio.c
index 5e541faac4..31dbf771b1 100644
--- a/libsrc/posixio.c
+++ b/libsrc/posixio.c
@@ -15,6 +15,7 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <string.h>
+#include <stdint.h>
 
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
@@ -120,7 +121,7 @@ static off_t nc_get_filelen(const int fd) {
   off_t flen;
 
 #ifdef HAVE_FILE_LENGTH_I64
-  __int64 file_len = 0;
+  int64_t file_len = 0;
   if ((file_len = _filelengthi64(fd)) < 0) {
     return file_len;
   }
@@ -1829,7 +1830,7 @@ ncio_px_filesize(ncio *nciop, off_t *filesizep)
 		Use _filelengthi64 isntead. */
 #ifdef HAVE_FILE_LENGTH_I64
 
-	__int64 file_len = 0;
+	int64_t file_len = 0;
 	if( (file_len = _filelengthi64(nciop->fd)) < 0) {
 		return errno;
 	}