diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index bee8bffb6e..2c2763d03c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-07-28  Tom de Vries  <tdevries@suse.de>
+
+	* eval.c (evaluate_subexp_for_sizeof): Interpret size of dynamic type
+	with undefined upper bound as <optimized out>.
+
 2018-07-27  Sergio Durigan Junior  <sergiodj@redhat.com>
 
 	* gcore.in: Rename variable "name" to "prefix".  Expand
diff --git a/gdb/eval.c b/gdb/eval.c
index 9db6e7c69d..0495a11bfd 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -3145,6 +3145,8 @@ evaluate_subexp_for_sizeof (struct expression *exp, int *pos,
 	{
 	  val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_NORMAL);
 	  type = value_type (val);
+	  if (TYPE_HIGH_BOUND_UNDEFINED (TYPE_INDEX_TYPE (type)))
+	    return allocate_optimized_out_value (size_type);
 	}
       else
 	(*pos) += 4;
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index f51e255e31..f3d212c3dd 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2018-07-28  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.base/vla-optimized-out-o3-strict.exp: New file.
+
 2018-07-26  Tom de Vries  <tdevries@suse.de>
 
 	* gdb.base/vla-optimized-out.c: Add comment about origin of test-case.
diff --git a/gdb/testsuite/gdb.base/vla-optimized-out-o3-strict.exp b/gdb/testsuite/gdb.base/vla-optimized-out-o3-strict.exp
new file mode 100644
index 0000000000..81ada875b3
--- /dev/null
+++ b/gdb/testsuite/gdb.base/vla-optimized-out-o3-strict.exp
@@ -0,0 +1,40 @@
+# Copyright 2018 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Check whether we can determine the size of an optimized-out vla.
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile vla-optimized-out.c \
+	  {debug optimize=-O3 additional_flags=-gstrict-dwarf}] } {
+    return -1
+}
+
+proc vla_optimized_out { } {
+    if ![runto f1] {
+	fail "can't run to f1"
+	return
+    }
+
+    gdb_test "p a" \
+	{ = <optimized out>} \
+	"printed optimized out vla"
+
+    gdb_test "p sizeof (a)" \
+	{ = <optimized out>} \
+	"printed optimized out size of optimized out vla"
+}
+
+vla_optimized_out