diff --git a/synapse/storage/data_stores/main/devices.py b/synapse/storage/data_stores/main/devices.py
index ea0503476f3fb61f294980b30e99c92d50bfa759..b7617efb80a8ee280380926c59565afb5870ae7d 100644
--- a/synapse/storage/data_stores/main/devices.py
+++ b/synapse/storage/data_stores/main/devices.py
@@ -320,6 +320,11 @@ class DeviceWorkerStore(SQLBaseStore):
                     device_display_name = device.get("device_display_name", None)
                     if device_display_name:
                         result["device_display_name"] = device_display_name
+                    if "signatures" in device:
+                        for sig_user_id, sigs in device["signatures"].items():
+                            result["keys"].setdefault("signatures", {}).setdefault(
+                                sig_user_id, {}
+                            ).update(sigs)
                 else:
                     result["deleted"] = True
 
@@ -524,6 +529,11 @@ class DeviceWorkerStore(SQLBaseStore):
                 device_display_name = device.get("device_display_name", None)
                 if device_display_name:
                     result["device_display_name"] = device_display_name
+                if "signatures" in device:
+                    for sig_user_id, sigs in device["signatures"].items():
+                        result["keys"].setdefault("signatures", {}).setdefault(
+                            sig_user_id, {}
+                        ).update(sigs)
 
                 results.append(result)