diff --git a/sgx-bwmsgsv2.rb b/sgx-bwmsgsv2.rb
index c706d248ef86a4a89538f1843b90425c31dccaa0..c2cc46007dab43847426cdf4ea6d9db96d0aa49a 100755
--- a/sgx-bwmsgsv2.rb
+++ b/sgx-bwmsgsv2.rb
@@ -446,6 +446,14 @@ module SGXbwmsgsv2
 			])
 		end
 
+		if body =~ /\u2063/
+			return EMPromise.reject([
+				:wait,
+				'recipient-unavailable',
+				'Please contact JMP support about your message'
+			])
+		end
+
 		segment_size = body.ascii_only? ? 160 : 70
 		if !murl && ENV["MMS_PATH"] && body.length > segment_size*3
 			file = Multibases.pack(
diff --git a/test/property/test_invisible_separator.rb b/test/property/test_invisible_separator.rb
new file mode 100644
index 0000000000000000000000000000000000000000..e3994d056e1b2bd37402cf1688846ebf1f607691
--- /dev/null
+++ b/test/property/test_invisible_separator.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require_relative "../../sgx-bwmsgsv2"
+require "rantly/minitest_extensions"
+require_relative "rantly_extensions/data_extensions"
+
+class InvisibleSeparatorPropertyTest < Minitest::Test
+	BW_MESSAGES_URL =
+		"https://messaging.bandwidth.com/api/v2/users/account/messages"
+
+	def setup
+		reset_stanzas!
+		reset_redis!
+	end
+
+	def test_message_containing_invisible_separator_is_rejected
+		property_of {
+			words = array(range(1, 6)) { sized(range(3, 10)) { string(:alnum) } }
+			guard(words.none? { |w| BADWORD_LIST.include?(w.downcase) })
+			chars = words.join(" ").chars
+			insertions = range(1, 3)
+			insertions.times { chars.insert(range(0, chars.length), "\u2063") }
+			body = chars.join
+
+			dest = nanpa_phone
+			[body, dest]
+		}.check { |body, dest|
+			reset_stanzas!
+			reset_redis!
+
+			stub_request(:post, BW_MESSAGES_URL).to_return(
+				status: 201,
+				body: JSON.dump(id: "bw-msg-stub")
+			)
+
+			m = Blather::Stanza::Message.new("#{dest}@component", body)
+			m.from = "test@example.com"
+			process_stanza(m)
+
+			assert_equal 1, written.length,
+			             "Expected exactly one error stanza for body: #{body.inspect}"
+
+			stanza = Blather::XMPPNode.parse(written.first.to_xml)
+			assert stanza.error?,
+			       "Expected error stanza for body: #{body.inspect}"
+
+			error = stanza.find_first("error")
+			assert_equal "wait", error["type"],
+			             "Expected error type 'wait' for body: #{body.inspect}"
+			assert_equal "recipient-unavailable", xmpp_error_name(error),
+			             "Expected 'recipient-unavailable' for body: #{body.inspect}"
+		}
+	end
+	em :test_message_containing_invisible_separator_is_rejected
+
+	def test_message_without_invisible_separator_is_not_rejected_as_unavailable
+		property_of {
+			words = array(range(1, 6)) { sized(range(3, 10)) { string(:alnum) } }
+			guard(words.none? { |w| BADWORD_LIST.include?(w.downcase) })
+			body = words.join(" ")
+
+			dest = nanpa_phone
+			[body, dest]
+		}.check { |body, dest|
+			reset_stanzas!
+			reset_redis!
+
+			stub_request(:post, BW_MESSAGES_URL).to_return(
+				status: 201,
+				body: JSON.dump(id: "bw-msg-stub")
+			)
+
+			m = Blather::Stanza::Message.new("#{dest}@component", body)
+			m.from = "test@example.com"
+			process_stanza(m)
+
+			written.each do |response|
+				stanza = Blather::XMPPNode.parse(response.to_xml)
+				next unless stanza.error?
+
+				error = stanza.find_first("error")
+				msg = "Clean message rejected as " \
+					"recipient-unavailable: #{body.inspect}"
+				refute_equal "recipient-unavailable",
+				             xmpp_error_name(error), msg
+			end
+		}
+	end
+	em :test_message_without_invisible_separator_is_not_rejected_as_unavailable
+end