diff --git a/src/mango/src/mango_idx_view.erl b/src/mango/src/mango_idx_view.erl
index d1650e987cc..29895fbf9c6 100644
--- a/src/mango/src/mango_idx_view.erl
+++ b/src/mango/src/mango_idx_view.erl
@@ -417,7 +417,7 @@ range(_, _, LCmp, Low, HCmp, High) ->
 % beginsWith requires both a high and low bound
 range({[{<<"$beginsWith">>, Arg}]}, LCmp, Low, HCmp, High) ->
     {LCmp0, Low0, HCmp0, High0} = range({[{<<"$gte">>, Arg}]}, LCmp, Low, HCmp, High),
-    range({[{<<"$lte">>, <<Arg/binary, 16#10FFFF>>}]}, LCmp0, Low0, HCmp0, High0);
+    range({[{<<"$lte">>, <<Arg/binary, 16#FFFF/utf8>>}]}, LCmp0, Low0, HCmp0, High0);
 range({[{<<"$lt">>, Arg}]}, LCmp, Low, HCmp, High) ->
     case range_pos(Low, Arg, High) of
         min ->
diff --git a/src/mango/src/mango_selector.erl b/src/mango/src/mango_selector.erl
index 93d3b10ca6c..24660e963f3 100644
--- a/src/mango/src/mango_selector.erl
+++ b/src/mango/src/mango_selector.erl
@@ -136,7 +136,10 @@ norm_ops({[{<<"$text">>, Arg}]}) when
 norm_ops({[{<<"$text">>, Arg}]}) ->
     ?MANGO_ERROR({bad_arg, '$text', Arg});
 norm_ops({[{<<"$beginsWith">>, Arg}]} = Cond) when is_binary(Arg) ->
-    Cond;
+    case couch_util:validate_utf8(Arg) of
+        true -> Cond;
+        false -> ?MANGO_ERROR({bad_arg, '$beginsWith', Arg})
+    end;
 % Not technically an operator but we pass it through here
 % so that this function accepts its own output. This exists
 % so that $text can have a field name value which simplifies
diff --git a/src/mango/test/25-beginswith-test.py b/src/mango/test/25-beginswith-test.py
index 3b5134b6514..919dcc661c4 100644
--- a/src/mango/test/25-beginswith-test.py
+++ b/src/mango/test/25-beginswith-test.py
@@ -54,7 +54,7 @@ def test_json_range(self):
 
         self.assertEqual(mrargs["start_key"], ["A"])
         end_key_bytes = to_utf8_bytes(mrargs["end_key"])
-        self.assertEqual(end_key_bytes, [b"A\xef\xbf\xbd", b"<MAX>"])
+        self.assertEqual(end_key_bytes, [b"A\xf4\x8f\xbf\xbf", b"<MAX>"])
 
     def test_compound_key(self):
         selector = {"name": "Eddie", "location": {"$beginsWith": "A"}}
@@ -62,7 +62,7 @@ def test_compound_key(self):
 
         self.assertEqual(mrargs["start_key"], ["Eddie", "A"])
         end_key_bytes = to_utf8_bytes(mrargs["end_key"])
-        self.assertEqual(end_key_bytes, [b"Eddie", b"A\xef\xbf\xbd", b"<MAX>"])
+        self.assertEqual(end_key_bytes, [b"Eddie", b"A\xf4\x8f\xbf\xbf", b"<MAX>"])
 
         docs = self.db.find(selector)
         self.assertEqual(len(docs), 1)
@@ -74,12 +74,12 @@ def test_sort(self):
             {
                 "sort": ["location"],
                 "start_key": [b"A"],
-                "end_key": [b"A\xef\xbf\xbd", b"<MAX>"],
+                "end_key": [b"A\xf4\x8f\xbf\xbf", b"<MAX>"],
                 "direction": "fwd",
             },
             {
                 "sort": [{"location": "desc"}],
-                "start_key": [b"A\xef\xbf\xbd", b"<MAX>"],
+                "start_key": [b"A\xf4\x8f\xbf\xbf", b"<MAX>"],
                 "end_key": [b"A"],
                 "direction": "rev",
             },
@@ -97,7 +97,7 @@ def test_all_docs_range(self):
 
         self.assertEqual(mrargs["start_key"], "a")
         end_key_bytes = to_utf8_bytes(mrargs["end_key"])
-        self.assertEqual(end_key_bytes, [b"a", b"\xef\xbf\xbd"])
+        self.assertEqual(end_key_bytes, [b"a", b"\xf4\x8f\xbf\xbf"])
 
     def test_no_index(self):
         selector = {"foo": {"$beginsWith": "a"}}