diff --git a/tests/csapi/apidoc_room_create_test.go b/tests/csapi/apidoc_room_create_test.go
index 7abc9b51..1b5e63bb 100644
--- a/tests/csapi/apidoc_room_create_test.go
+++ b/tests/csapi/apidoc_room_create_test.go
@@ -11,6 +11,7 @@ import (
 	"github.com/matrix-org/complement/helpers"
 	"github.com/matrix-org/complement/match"
 	"github.com/matrix-org/complement/must"
+	"github.com/matrix-org/complement/runtime"
 )
 
 func TestRoomCreate(t *testing.T) {
@@ -62,6 +63,89 @@ func TestRoomCreate(t *testing.T) {
 			content := alice.MustGetStateEventContent(t, roomID, "m.room.topic", "")
 			must.MatchGJSON(t, content, match.JSONKeyEqual("topic", "Test Room"))
 		})
+		// POST /createRoom makes a room with a topic and writes rich topic representation
+		t.Run("POST /createRoom makes a room with a topic and writes rich topic representation", func(t *testing.T) {
+			// Rich topics not implemented yet on Dendrite
+			runtime.SkipIf(t, runtime.Dendrite)
+
+			t.Parallel()
+
+			roomID := alice.MustCreateRoom(t, map[string]interface{}{
+				"topic":  "Test Room",
+				"preset": "public_chat",
+			})
+			content := alice.MustGetStateEventContent(t, roomID, "m.room.topic", "")
+			must.MatchGJSON(t, content, match.JSONKeyEqual("topic", "Test Room"))
+
+			// The plain text topic is duplicated into m.topic
+			must.MatchGJSON(t, content,
+				match.JSONKeyArrayOfSize("m\\.topic.m\\.text", 1),
+				match.JSONKeyPresent("m\\.topic.m\\.text.0.body"),
+				match.JSONKeyEqual("m\\.topic.m\\.text.0.body", "Test Room"))
+
+			// The mime type must be unset or text/plain
+			mime := content.Get("m\\.topic.m\\.text.0.mimetype")
+			if mime.Exists() {
+				must.Equal(t, mime.String(), "text/plain", "expected rich topic mimetype to be unset (defaults to text/plain) or explicitly set as text/plain")
+			}
+		})
+		// POST /createRoom makes a room with a topic via initial_state
+		t.Run("POST /createRoom makes a room with a topic via initial_state", func(t *testing.T) {
+			t.Parallel()
+
+			roomID := alice.MustCreateRoom(t, map[string]interface{}{
+				"initial_state": []map[string]interface{}{
+					{
+						"content": map[string]interface{}{
+							"topic": "Test Room",
+						},
+						"type":      "m.room.topic",
+						"state_key": "",
+					},
+				},
+				"preset": "public_chat",
+			})
+			content := alice.MustGetStateEventContent(t, roomID, "m.room.topic", "")
+			must.MatchGJSON(t, content, match.JSONKeyEqual("topic", "Test Room"))
+
+			// There is no m.topic property
+			must.MatchGJSON(t, content, match.JSONKeyMissing("m\\.topic"))
+		})
+		// POST /createRoom makes a room with a topic via initial_state overwritten by topic
+		t.Run("POST /createRoom makes a room with a topic via initial_state overwritten by topic", func(t *testing.T) {
+			// Rich topics not implemented yet on Dendrite
+			runtime.SkipIf(t, runtime.Dendrite)
+
+			t.Parallel()
+
+			roomID := alice.MustCreateRoom(t, map[string]interface{}{
+				"topic": "Test Room",
+				"initial_state": []map[string]interface{}{
+					{
+						"content": map[string]interface{}{
+							"topic": "Shenanigans",
+						},
+						"type":      "m.room.topic",
+						"state_key": "",
+					},
+				},
+				"preset": "public_chat",
+			})
+			content := alice.MustGetStateEventContent(t, roomID, "m.room.topic", "")
+			must.MatchGJSON(t, content, match.JSONKeyEqual("topic", "Test Room"))
+
+			// The plain text topic is duplicated into m.topic
+			must.MatchGJSON(t, content,
+				match.JSONKeyArrayOfSize("m\\.topic.m\\.text", 1),
+				match.JSONKeyPresent("m\\.topic.m\\.text.0.body"),
+				match.JSONKeyEqual("m\\.topic.m\\.text.0.body", "Test Room"))
+
+			// The mime type must be unset or text/plain
+			mime := content.Get("m\\.topic.m\\.text.0.mimetype")
+			if mime.Exists() {
+				must.Equal(t, mime.String(), "text/plain", "expected rich topic mimetype to be unset (defaults to text/plain) or explicitly set as text/plain")
+			}
+		})
 		// sytest: POST /createRoom makes a room with a name
 		t.Run("POST /createRoom makes a room with a name", func(t *testing.T) {
 			t.Parallel()