--- gcc/gimplify.c.jj	2012-12-20 19:13:00.000000000 +0100
+++ gcc/gimplify.c	2013-01-03 16:16:07.288707387 +0100
@@ -8180,6 +8180,26 @@ gimplify_one_sizepos (tree *expr_p, gimp
   *expr_p = unshare_expr (expr);
 
   gimplify_expr (expr_p, stmt_p, NULL, is_gimple_val, fb_rvalue);
+
+  /* Ensure we don't change an INTEGER_TYPE expression into e.g. ENUMERAL_TYPE
+     expression.  */
+  if (TREE_CODE (TREE_TYPE (*expr_p)) != TREE_CODE (TREE_TYPE (expr)))
+    {
+      gcc_checking_assert (useless_type_conversion_p (TREE_TYPE (expr),
+						      TREE_TYPE (*expr_p)));
+      if (TREE_CODE (*expr_p) == INTEGER_CST)
+	*expr_p = fold_convert (TREE_TYPE (expr), *expr_p);
+      else
+	{
+	  tree var = create_tmp_var (TREE_TYPE (expr), NULL);
+	  tree mod = build2 (INIT_EXPR, TREE_TYPE (var),
+			     var, unshare_expr (*expr_p));
+	  SET_EXPR_LOCATION (mod, EXPR_LOC_OR_HERE (*expr_p));
+	  gimplify_and_add (mod, stmt_p);
+	  ggc_free (mod);
+	  *expr_p = var;
+	}
+    }
 }
 
 /* Gimplify the body of statements of FNDECL and return a GIMPLE_BIND node
--- gcc/testsuite/gcc.c-torture/compile/pr55851.c.jj	2013-01-03 16:20:19.085284806 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr55851.c	2013-01-03 16:19:27.698571718 +0100
@@ -0,0 +1,12 @@
+/* PR middle-end/55851 */
+
+enum { A = 1UL, B = -1UL } var = A;
+void foo (char *);
+
+void
+test (void)
+{
+  char vla[1][var];
+  vla[0][0] = 1;
+  foo (&vla[0][0]);
+}