diff --git a/changelog.d/9719.doc b/changelog.d/9719.doc
new file mode 100644
index 000000000..f018606dd
--- /dev/null
+++ b/changelog.d/9719.doc
@@ -0,0 +1 @@
+Make the allowed_local_3pids regex example in the sample config stricter.
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index c73ea6b16..b0bf98774 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -1246,9 +1246,9 @@ account_validity:
 #
 #allowed_local_3pids:
 #  - medium: email
-#    pattern: '.*@matrix\.org'
+#    pattern: '^[^@]+@matrix\.org$'
 #  - medium: email
-#    pattern: '.*@vector\.im'
+#    pattern: '^[^@]+@vector\.im$'
 #  - medium: msisdn
 #    pattern: '\+44'
 
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index ead007ba5..f27d1e14a 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -298,9 +298,9 @@ class RegistrationConfig(Config):
         #
         #allowed_local_3pids:
         #  - medium: email
-        #    pattern: '.*@matrix\\.org'
+        #    pattern: '^[^@]+@matrix\\.org$'
         #  - medium: email
-        #    pattern: '.*@vector\\.im'
+        #    pattern: '^[^@]+@vector\\.im$'
         #  - medium: msisdn
         #    pattern: '\\+44'