diff --git a/frontend/syntax.asdl b/frontend/syntax.asdl
index 386a29634c..94de319b3d 100644
--- a/frontend/syntax.asdl
+++ b/frontend/syntax.asdl
@@ -112,7 +112,7 @@ module syntax
   | ArrayIndex(arith_expr expr)
 
   suffix_op = 
-    Nullary(id op_id)  -- ${x@Q} or ${!prefix@} (which also has prefix_op)
+    Nullary %Token  -- ${x@Q} or ${!prefix@} (which also has prefix_op)
   | Unary(id op_id, word arg_word)  -- e.g. ${v:-default}
     -- TODO: token for / to attribute errors
   | PatSub(word pat, word? replace, id replace_mode)
diff --git a/osh/word_eval.py b/osh/word_eval.py
index 0b9ee333af..083811d97b 100644
--- a/osh/word_eval.py
+++ b/osh/word_eval.py
@@ -7,7 +7,7 @@
     braced_var_sub, Token,
     word, word_e, word_t, compound_word,
     bracket_op_e, bracket_op__ArrayIndex, bracket_op__WholeArray,
-    suffix_op_e, suffix_op__Nullary, suffix_op__PatSub, suffix_op__Slice,
+    suffix_op_e, suffix_op__PatSub, suffix_op__Slice,
     suffix_op__Unary,
     sh_array_literal, single_quoted, double_quoted, simple_var_sub,
     command_sub,
@@ -862,9 +862,9 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
         names.sort()
         val = value.MaybeStrArray(names)  # type: value_t
 
-        suffix_op = cast(suffix_op__Nullary, part.suffix_op)
+        suffix_op = cast(Token, part.suffix_op)
         # "${!prefix@}" is the only one that doesn't decay
-        maybe_decay_array = not (quoted and suffix_op.op_id == Id.VOp3_At)
+        maybe_decay_array = not (quoted and suffix_op.id == Id.VOp3_At)
         name_query = True
       else:
         var_name = part.token.val
@@ -995,18 +995,29 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
       UP_op = op
       with tagswitch(op) as case:
         if case(suffix_op_e.Nullary):
-          op = cast(suffix_op__Nullary, UP_op)
-          if op.op_id == Id.VOp0_P:
+          op = cast(Token, UP_op)
+          op_id = op.id
+          if op_id == Id.VOp0_P:
             prompt = self.prompt_ev.EvalPrompt(val)
             # readline gets rid of these, so we should too.
             p = prompt.replace('\x01', '').replace('\x02', '')
             val = value.Str(p)
-          elif op.op_id == Id.VOp0_Q:
+          elif op_id == Id.VOp0_Q:
             assert val.tag_() == value_e.Str, val
             val = cast(value__Str, val)
             val = value.Str(string_ops.ShellQuote(val.s))
+          elif op_id == Id.VOp0_a:
+            # We're ONLY simluating -a and -A, not -r -x -n for now.  See
+            # spec/ble-idioms.test.sh.
+            s = ''
+            with tagswitch(val) as case:
+              if case(value_e.MaybeStrArray):
+                s += 'a'
+              elif case(value_e.AssocArray):
+                s += 'A'
+            val = value.Str(s)
           else:
-            raise NotImplementedError(op.op_id)
+            e_die('Var op %r not implemented', op.val, token=op)
 
         elif case(suffix_op_e.Unary):
           op = cast(suffix_op__Unary, UP_op)
diff --git a/osh/word_parse.py b/osh/word_parse.py
index 8b5a4578c3..3bedfcf809 100644
--- a/osh/word_parse.py
+++ b/osh/word_parse.py
@@ -334,8 +334,7 @@ def _ParseVarExpr(self, arg_lex_mode, allow_query=False):
       part.suffix_op = suffix_op.Unary(op_id, arg_word)
 
     elif op_kind == Kind.VOp0:
-      op_id = self.token_type
-      part.suffix_op = suffix_op.Nullary(op_id)
+      part.suffix_op = self.cur_token  # Nullary
       self._Next(lex_mode_e.VSub_2)  # Expecting }
       self._Peek()
 
@@ -373,8 +372,7 @@ def _ParseVarExpr(self, arg_lex_mode, allow_query=False):
 
     elif op_kind == Kind.VOp3:
       if allow_query:
-        op_id = self.token_type
-        part.suffix_op = suffix_op.Nullary(op_id)
+        part.suffix_op = self.cur_token  # Nullary
         self._Next(lex_mode_e.VSub_2)  # Expecting }
         self._Peek()
       else:
diff --git a/spec/ble-idioms.test.sh b/spec/ble-idioms.test.sh
index 502e3f70f8..fd03fc4f27 100644
--- a/spec/ble-idioms.test.sh
+++ b/spec/ble-idioms.test.sh
@@ -136,3 +136,26 @@ echo c_x=$c_x c_y=$c_y
 c_x=3 c_y=4
 c_x=7 c_y=24
 ## END
+
+#### is-array with ${var@a}
+case $SH in (mksh|ash) exit 1 ;; esac
+
+function ble/is-array { [[ ${!1@a} == *a* ]]; }
+
+ble/is-array undef
+echo undef $?
+
+string=''
+ble/is-array string
+echo string $?
+
+array=(one two three)
+ble/is-array array
+echo array $?
+## STDOUT:
+undef 1
+string 1
+array 0
+## END
+## N-I zsh/mksh/ash status: 1
+## N-I zsh/mksh/ash stdout-json: ""