diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d75f1a834e6..14f899c1881 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2018-02-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/84558
+	* constexpr.c (cxx_eval_vec_init_1): For reuse, treat NULL eltinit like
+	a valid constant initializer.  Formatting fixes.
+
 2018-02-26  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/84540
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 26d0d099a05..b3de62a5bea 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -2959,9 +2959,8 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init,
 	  if (!lvalue_p (init))
 	    eltinit = move (eltinit);
 	  eltinit = force_rvalue (eltinit, tf_warning_or_error);
-	  eltinit = (cxx_eval_constant_expression
-		     (&new_ctx, eltinit, lval,
-		      non_constant_p, overflow_p));
+	  eltinit = cxx_eval_constant_expression (&new_ctx, eltinit, lval,
+						  non_constant_p, overflow_p);
 	}
       if (*non_constant_p && !ctx->quiet)
 	break;
@@ -2974,12 +2973,13 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init,
       else
 	CONSTRUCTOR_APPEND_ELT (*p, idx, eltinit);
       /* Reuse the result of cxx_eval_constant_expression call
-	  from the first iteration to all others if it is a constant
-	  initializer that doesn't require relocations.  */
+	 from the first iteration to all others if it is a constant
+	 initializer that doesn't require relocations.  */
       if (reuse
 	  && max > 1
-	  && (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
-	      == null_pointer_node))
+	  && (eltinit == NULL_TREE
+	      || (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
+		  == null_pointer_node)))
 	{
 	  if (new_ctx.ctor != ctx->ctor)
 	    eltinit = new_ctx.ctor;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f050086b8bb..11d79943b9c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/84558
+	* g++.dg/cpp1y/pr84558.C: New test.
+
 2018-02-26  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/84540
diff --git a/gcc/testsuite/g++.dg/cpp1y/pr84558.C b/gcc/testsuite/g++.dg/cpp1y/pr84558.C
new file mode 100644
index 00000000000..40d7ef68561
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/pr84558.C
@@ -0,0 +1,6 @@
+// PR c++/84558
+// { dg-do compile { target c++14 } }
+
+struct A { static int i; constexpr A () { i = 0; } };
+struct B { A a[2][3][4]; };
+B b;