diff --git a/changelog.d/15554.misc b/changelog.d/15554.misc
new file mode 100644
index 000000000000..002e3f53157d
--- /dev/null
+++ b/changelog.d/15554.misc
@@ -0,0 +1 @@
+Use account data constants in more places.
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index c56b2f256150..cde9a2ecefb3 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -257,6 +257,7 @@ class AccountDataTypes:
     DIRECT: Final = "m.direct"
     IGNORED_USER_LIST: Final = "m.ignored_user_list"
     TAG: Final = "m.tag"
+    PUSH_RULES: Final = "m.push_rules"
 
 
 class HistoryVisibility:
diff --git a/synapse/handlers/read_marker.py b/synapse/handlers/read_marker.py
index 05122fd5a6b4..6d35e6188084 100644
--- a/synapse/handlers/read_marker.py
+++ b/synapse/handlers/read_marker.py
@@ -15,6 +15,7 @@
 import logging
 from typing import TYPE_CHECKING
 
+from synapse.api.constants import ReceiptTypes
 from synapse.util.async_helpers import Linearizer
 
 if TYPE_CHECKING:
@@ -42,7 +43,7 @@ async def received_client_read_marker(
 
         async with self.read_marker_linearizer.queue((room_id, user_id)):
             existing_read_marker = await self.store.get_account_data_for_room_and_type(
-                user_id, room_id, "m.fully_read"
+                user_id, room_id, ReceiptTypes.FULLY_READ
             )
 
             should_update = True
@@ -56,5 +57,5 @@ async def received_client_read_marker(
             if should_update:
                 content = {"event_id": event_id}
                 await self.account_data_handler.add_account_data_to_room(
-                    user_id, room_id, "m.fully_read", content
+                    user_id, room_id, ReceiptTypes.FULLY_READ, content
                 )
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 64d298408d21..cc05b0afa0f5 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -1777,18 +1777,18 @@ async def _generate_sync_entry_for_account_data(
 
             if push_rules_changed:
                 global_account_data = dict(global_account_data)
-                global_account_data["m.push_rules"] = await self.push_rules_for_user(
-                    sync_config.user
-                )
+                global_account_data[
+                    AccountDataTypes.PUSH_RULES
+                ] = await self.push_rules_for_user(sync_config.user)
         else:
             all_global_account_data = await self.store.get_global_account_data_for_user(
                 user_id
             )
 
             global_account_data = dict(all_global_account_data)
-            global_account_data["m.push_rules"] = await self.push_rules_for_user(
-                sync_config.user
-            )
+            global_account_data[
+                AccountDataTypes.PUSH_RULES
+            ] = await self.push_rules_for_user(sync_config.user)
 
         account_data_for_user = (
             await sync_config.filter_collection.filter_global_account_data(
diff --git a/synapse/rest/client/account_data.py b/synapse/rest/client/account_data.py
index 43193ad08644..8eebb21c7615 100644
--- a/synapse/rest/client/account_data.py
+++ b/synapse/rest/client/account_data.py
@@ -15,6 +15,7 @@
 import logging
 from typing import TYPE_CHECKING, Tuple
 
+from synapse.api.constants import ReceiptTypes
 from synapse.api.errors import AuthError, Codes, NotFoundError, SynapseError
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
@@ -166,7 +167,7 @@ async def on_PUT(
 
         body = parse_json_object_from_request(request)
 
-        if account_data_type == "m.fully_read":
+        if account_data_type == ReceiptTypes.FULLY_READ:
             raise SynapseError(
                 405,
                 "Cannot set m.fully_read through this API."