diff --git a/changelog.d/15781.bugfix b/changelog.d/15781.bugfix
new file mode 100644
index 000000000000..5faf59afee0c
--- /dev/null
+++ b/changelog.d/15781.bugfix
@@ -0,0 +1 @@
+Fix a bug in push rules handling leading to an invalid (per spec) `is_user_mention` rule sent to clients. Also fix wrong rule names for `is_user_mention` and `is_room_mention`.
\ No newline at end of file
diff --git a/rust/src/push/base_rules.rs b/rust/src/push/base_rules.rs
index 9d6c304d9285..7eea9313f038 100644
--- a/rust/src/push/base_rules.rs
+++ b/rust/src/push/base_rules.rs
@@ -142,7 +142,7 @@ pub const BASE_APPEND_OVERRIDE_RULES: &[PushRule] = &[
         default_enabled: true,
     },
     PushRule {
-        rule_id: Cow::Borrowed("global/override/.m.is_user_mention"),
+        rule_id: Cow::Borrowed("global/override/.m.rule.is_user_mention"),
         priority_class: 5,
         conditions: Cow::Borrowed(&[Condition::Known(
             KnownCondition::ExactEventPropertyContainsType(EventPropertyIsTypeCondition {
@@ -163,7 +163,7 @@ pub const BASE_APPEND_OVERRIDE_RULES: &[PushRule] = &[
         default_enabled: true,
     },
     PushRule {
-        rule_id: Cow::Borrowed("global/override/.m.is_room_mention"),
+        rule_id: Cow::Borrowed("global/override/.m.rule.is_room_mention"),
         priority_class: 5,
         conditions: Cow::Borrowed(&[
             Condition::Known(KnownCondition::EventPropertyIs(EventPropertyIsCondition {
diff --git a/synapse/push/clientformat.py b/synapse/push/clientformat.py
index 88b52c26a008..735cef0aed76 100644
--- a/synapse/push/clientformat.py
+++ b/synapse/push/clientformat.py
@@ -41,12 +41,7 @@ def format_push_rules_for_user(
 
         rulearray.append(template_rule)
 
-        for type_key in ("pattern", "value"):
-            type_value = template_rule.pop(f"{type_key}_type", None)
-            if type_value == "user_id":
-                template_rule[type_key] = user.to_string()
-            elif type_value == "user_localpart":
-                template_rule[type_key] = user.localpart
+        _convert_type_to_value(template_rule, user)
 
         template_rule["enabled"] = enabled
 
@@ -63,19 +58,20 @@ def format_push_rules_for_user(
         for c in template_rule["conditions"]:
             c.pop("_cache_key", None)
 
-            pattern_type = c.pop("pattern_type", None)
-            if pattern_type == "user_id":
-                c["pattern"] = user.to_string()
-            elif pattern_type == "user_localpart":
-                c["pattern"] = user.localpart
-
-            sender_type = c.pop("sender_type", None)
-            if sender_type == "user_id":
-                c["sender"] = user.to_string()
+            _convert_type_to_value(c, user)
 
     return rules
 
 
+def _convert_type_to_value(rule_or_cond: Dict[str, Any], user: UserID) -> None:
+    for type_key in ("pattern", "value"):
+        type_value = rule_or_cond.pop(f"{type_key}_type", None)
+        if type_value == "user_id":
+            rule_or_cond[type_key] = user.to_string()
+        elif type_value == "user_localpart":
+            rule_or_cond[type_key] = user.localpart
+
+
 def _add_empty_priority_class_arrays(d: Dict[str, list]) -> Dict[str, list]:
     for pc in PRIORITY_CLASS_MAP.keys():
         d[pc] = []
diff --git a/tests/rest/client/test_push_rule_attrs.py b/tests/rest/client/test_push_rule_attrs.py
index 4f875b92898e..5aca74475f6f 100644
--- a/tests/rest/client/test_push_rule_attrs.py
+++ b/tests/rest/client/test_push_rule_attrs.py
@@ -412,3 +412,70 @@ def test_actions_404_when_put_non_existent_server_rule(self) -> None:
         )
         self.assertEqual(channel.code, 404)
         self.assertEqual(channel.json_body["errcode"], Codes.NOT_FOUND)
+
+    def test_contains_user_name(self) -> None:
+        """
+        Tests that `contains_user_name` rule is present and have proper value in `pattern`.
+        """
+        username = "bob"
+        self.register_user(username, "pass")
+        token = self.login(username, "pass")
+
+        channel = self.make_request(
+            "GET",
+            "/pushrules/global/content/.m.rule.contains_user_name",
+            access_token=token,
+        )
+
+        self.assertEqual(channel.code, 200)
+
+        self.assertEqual(
+            {
+                "rule_id": ".m.rule.contains_user_name",
+                "default": True,
+                "enabled": True,
+                "pattern": username,
+                "actions": [
+                    "notify",
+                    {"set_tweak": "highlight"},
+                    {"set_tweak": "sound", "value": "default"},
+                ],
+            },
+            channel.json_body,
+        )
+
+    def test_is_user_mention(self) -> None:
+        """
+        Tests that `is_user_mention` rule is present and have proper value in `value`.
+        """
+        user = self.register_user("bob", "pass")
+        token = self.login("bob", "pass")
+
+        channel = self.make_request(
+            "GET",
+            "/pushrules/global/override/.m.rule.is_user_mention",
+            access_token=token,
+        )
+
+        self.assertEqual(channel.code, 200)
+
+        self.assertEqual(
+            {
+                "rule_id": ".m.rule.is_user_mention",
+                "default": True,
+                "enabled": True,
+                "conditions": [
+                    {
+                        "kind": "event_property_contains",
+                        "key": "content.m\\.mentions.user_ids",
+                        "value": user,
+                    }
+                ],
+                "actions": [
+                    "notify",
+                    {"set_tweak": "highlight"},
+                    {"set_tweak": "sound", "value": "default"},
+                ],
+            },
+            channel.json_body,
+        )