diff --git a/gcc/ada/gcc-interface/utils.c b/gcc/ada/gcc-interface/utils.c
index 381d71b..732435b 100644
--- a/gcc/ada/gcc-interface/utils.c
+++ b/gcc/ada/gcc-interface/utils.c
@@ -382,7 +382,7 @@ gnat_poplevel (void)
   tree block = level->block;
 
   BLOCK_VARS (block) = nreverse (BLOCK_VARS (block));
-  BLOCK_SUBBLOCKS (block) = nreverse (BLOCK_SUBBLOCKS (block));
+  BLOCK_SUBBLOCKS (block) = blocks_nreverse (BLOCK_SUBBLOCKS (block));
 
   /* If this is a function-level BLOCK don't do anything.  Otherwise, if there
      are no variables free the block and merge its subblocks into those of its
diff --git a/gcc/tree.c b/gcc/tree.c
index f401145..e67a00c 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -2108,6 +2108,9 @@ nreverse (tree t)
   tree prev = 0, decl, next;
   for (decl = t; decl; decl = next)
     {
+      /* We shouldn't be using this function to reverse BLOCK chains; we
+	 have blocks_nreverse for that.  */
+      gcc_checking_assert (TREE_CODE (decl) != BLOCK);
       next = TREE_CHAIN (decl);
       TREE_CHAIN (decl) = prev;
       prev = decl;