diff --git a/src/validator/validator_impl.cc b/src/validator/validator_impl.cc
index 16da3e3bd9..ecad8efef7 100644
--- a/src/validator/validator_impl.cc
+++ b/src/validator/validator_impl.cc
@@ -318,9 +318,9 @@ bool ValidatorImpl::ValidateConstructedTypes(
               return false;
             }
             if (!st->IsBlockDecorated()) {
-              add_error(member->source(), "v-0031",
+              add_error(member->source(), "v-0015",
                         "a struct containing a runtime-sized array "
-                        "must be in the 'storage' storage class: '" +
+                        "requires the [[block]] attribute: '" +
                             program_->Symbols().NameFor(st->symbol()) + "'");
               return false;
             }
diff --git a/src/validator/validator_type_test.cc b/src/validator/validator_type_test.cc
index 306182a674..5f136eaadf 100644
--- a/src/validator/validator_type_test.cc
+++ b/src/validator/validator_type_test.cc
@@ -79,8 +79,8 @@ TEST_F(ValidatorTypeTest, RuntimeArrayIsLastNoBlock_Fail) {
 
   EXPECT_FALSE(v.ValidateConstructedTypes(program->AST().ConstructedTypes()));
   EXPECT_EQ(v.error(),
-            "v-0031: a struct containing a runtime-sized array must be "
-            "in the 'storage' storage class: 'Foo'");
+            "v-0015: a struct containing a runtime-sized array requires the "
+            "[[block]] attribute: 'Foo'");
 }
 
 TEST_F(ValidatorTypeTest, RuntimeArrayIsNotLast_Fail) {