diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 131da1a4ae4..1381a23449e 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -247,9 +247,12 @@ build_zero_init_1 (tree type, tree nelts, bool static_storage_p,
 
       /* Iterate over the array elements, building initializations.  */
       if (nelts)
-	max_index = fold_build2_loc (input_location,
-				 MINUS_EXPR, TREE_TYPE (nelts),
-				 nelts, integer_one_node);
+	max_index = fold_build2_loc (input_location, MINUS_EXPR,
+				     TREE_TYPE (nelts), nelts,
+				     build_one_cst (TREE_TYPE (nelts)));
+      /* Treat flexible array members like [0] arrays.  */
+      else if (TYPE_DOMAIN (type) == NULL_TREE)
+	max_index = build_minus_one_cst (sizetype);
       else
 	max_index = array_type_nelts (type);
 
@@ -261,20 +264,19 @@ build_zero_init_1 (tree type, tree nelts, bool static_storage_p,
 
       /* A zero-sized array, which is accepted as an extension, will
 	 have an upper bound of -1.  */
-      if (!tree_int_cst_equal (max_index, integer_minus_one_node))
+      if (!integer_minus_onep (max_index))
 	{
 	  constructor_elt ce;
 
 	  /* If this is a one element array, we just use a regular init.  */
-	  if (tree_int_cst_equal (size_zero_node, max_index))
+	  if (integer_zerop (max_index))
 	    ce.index = size_zero_node;
 	  else
 	    ce.index = build2 (RANGE_EXPR, sizetype, size_zero_node,
-				max_index);
+			       max_index);
 
-	  ce.value = build_zero_init_1 (TREE_TYPE (type),
-					 /*nelts=*/NULL_TREE,
-					 static_storage_p, NULL_TREE);
+	  ce.value = build_zero_init_1 (TREE_TYPE (type), /*nelts=*/NULL_TREE,
+					static_storage_p, NULL_TREE);
 	  if (ce.value)
 	    {
 	      vec_alloc (v, 1);
diff --git a/gcc/testsuite/g++.dg/ext/flexary38.C b/gcc/testsuite/g++.dg/ext/flexary38.C
new file mode 100644
index 00000000000..4fa987bcb41
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/flexary38.C
@@ -0,0 +1,18 @@
+// PR c++/99033
+// { dg-do compile }
+// { dg-options "" }
+
+struct T { int t; };
+struct S { char c; int T::*b[]; } a;
+struct U { char c; int T::*b[0]; } b;
+struct V { char c; int T::*b[1]; } c;
+struct W { char c; int T::*b[2]; } d;
+
+void
+foo ()
+{
+  a.c = 1;
+  b.c = 2;
+  c.c = 3;
+  d.c = 4;
+}