diff --git a/CHANGELOG.md b/CHANGELOG.md
index 23975fda..23da4d4f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ All notable changes to this project will be documented in this file.
 ## Improvements
 - Add a tooltip to the 'confirmation link' label (#436)
 - Update API to allow specifying channels by names (#440)
+- When saving a phone number, remove any invisible unicode characers
 
 ## v1.17.0 - 2020-10-14
 
diff --git a/hc/front/forms.py b/hc/front/forms.py
index fd9f0a32..b5f33626 100644
--- a/hc/front/forms.py
+++ b/hc/front/forms.py
@@ -1,12 +1,12 @@
 from datetime import timedelta as td
 import json
+import re
 from urllib.parse import quote, urlencode
 
 from django import forms
 from django.forms import URLField
 from django.conf import settings
 from django.core.exceptions import ValidationError
-from django.core.validators import RegexValidator
 from hc.front.validators import (
     CronExpressionValidator,
     TimezoneValidator,
@@ -193,18 +193,22 @@ class AddShellForm(forms.Form):
         return json.dumps(dict(self.cleaned_data), sort_keys=True)
 
 
-phone_validator = RegexValidator(
-    regex="^\+\d{5,15}$", message="Invalid phone number format."
-)
-
-
 class AddSmsForm(forms.Form):
     error_css_class = "has-error"
     label = forms.CharField(max_length=100, required=False)
-    value = forms.CharField(max_length=16, validators=[phone_validator])
+    value = forms.CharField()
     down = forms.BooleanField(required=False, initial=True)
     up = forms.BooleanField(required=False, initial=True)
 
+    def clean_value(self):
+        v = self.cleaned_data["value"]
+
+        stripped = v.encode("ascii", "ignore").decode("ascii")
+        if not re.match(r"^\+\d{5,15}$", stripped):
+            raise forms.ValidationError("Invalid phone number format.")
+
+        return stripped
+
 
 class ChannelNameForm(forms.Form):
     name = forms.CharField(max_length=100, required=False)
diff --git a/hc/front/tests/test_add_sms.py b/hc/front/tests/test_add_sms.py
index eaa02842..73a6fe10 100644
--- a/hc/front/tests/test_add_sms.py
+++ b/hc/front/tests/test_add_sms.py
@@ -37,11 +37,11 @@ class AddSmsTestCase(BaseTestCase):
         self.assertEqual(c.project, self.project)
 
     def test_it_rejects_bad_number(self):
-        form = {"value": "not a phone number address"}
-
-        self.client.login(username="alice@example.org", password="password")
-        r = self.client.post(self.url, form)
-        self.assertContains(r, "Invalid phone number format.")
+        for v in ["not a phone number address", False, 15, "+123456789A"]:
+            form = {"value": v}
+            self.client.login(username="alice@example.org", password="password")
+            r = self.client.post(self.url, form)
+            self.assertContains(r, "Invalid phone number format.")
 
     def test_it_trims_whitespace(self):
         form = {"value": "   +1234567890   "}
@@ -65,3 +65,13 @@ class AddSmsTestCase(BaseTestCase):
         self.client.login(username="bob@example.org", password="password")
         r = self.client.get(self.url)
         self.assertEqual(r.status_code, 403)
+
+    def test_it_strips_invisible_formatting_characters(self):
+        form = {"label": "My Phone", "value": "\u202c+1234567890\u202c"}
+
+        self.client.login(username="alice@example.org", password="password")
+        r = self.client.post(self.url, form)
+        self.assertRedirects(r, self.channels_url)
+
+        c = Channel.objects.get()
+        self.assertEqual(c.phone_number, "+1234567890")