diff --git a/libgfortran/ChangeLog b/libgfortran/ChangeLog
index 3e8173913a0..986b2b0a31e 100644
--- a/libgfortran/ChangeLog
+++ b/libgfortran/ChangeLog
@@ -1,3 +1,10 @@
+2017-12-03  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
+
+	Backport from trunk
+	PR libgfortran/83168
+	* io/write.c (select_string): Bump size by one to avoid
+	overrun.
+
 2017-12-03  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 	    Dominique d'Humieres  <dominiq@lps.ens.fr>
 
diff --git a/libgfortran/io/write.c b/libgfortran/io/write.c
index f80a7c36265..d483de125f7 100644
--- a/libgfortran/io/write.c
+++ b/libgfortran/io/write.c
@@ -1552,7 +1552,7 @@ select_string (st_parameter_dt *dtp, const fnode *f, char *buf, size_t *size,
 	       int kind)
 {
   char *result;
-  *size = size_from_kind (dtp, f, kind) + f->u.real.d;
+  *size = size_from_kind (dtp, f, kind) + f->u.real.d + 1;
   if (*size > BUF_STACK_SZ)
      result = xmalloc (*size);
   else