diff --git a/libgfortran/ChangeLog b/libgfortran/ChangeLog
index f34b4df785a..d29f4f46100 100644
--- a/libgfortran/ChangeLog
+++ b/libgfortran/ChangeLog
@@ -1,3 +1,8 @@
+2017-07-24  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	* io/unix.c (buf_write):  Return early if there is
+	nothing to write.
+
 2017-06-09  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	* intrinsics/eoshift2.c (eoshift2):  Use memcpy
diff --git a/libgfortran/io/unix.c b/libgfortran/io/unix.c
index c76b427387a..61e9f7997b2 100644
--- a/libgfortran/io/unix.c
+++ b/libgfortran/io/unix.c
@@ -582,6 +582,9 @@ buf_read (unix_stream *s, void *buf, ssize_t nbyte)
 static ssize_t
 buf_write (unix_stream *s, const void *buf, ssize_t nbyte)
 {
+  if (nbyte == 0)
+    return 0;
+
   if (s->ndirty == 0)
     s->buffer_offset = s->logical_offset;