diff --git a/event/capabilities.d.ts b/event/capabilities.d.ts
index 1c5d533d..4cf29de7 100644
--- a/event/capabilities.d.ts
+++ b/event/capabilities.d.ts
@@ -17,6 +17,9 @@ export interface RoomFeatures {
 	 */
 	file?: Record<CapabilityMsgType, FileFeatures>
 
+	/** Maximum length of normal text messages. */
+	max_text_length?: integer
+
 	/** Whether location messages (`m.location`) are supported. */
 	location_message?: CapabilitySupportLevel
 	/** Whether polls are supported. */
diff --git a/event/capabilities.go b/event/capabilities.go
index 6a9b0b56..9c9eb09a 100644
--- a/event/capabilities.go
+++ b/event/capabilities.go
@@ -30,6 +30,8 @@ type RoomFeatures struct {
 	Formatting FormattingFeatureMap `json:"formatting,omitempty"`
 	File       FileFeatureMap       `json:"file,omitempty"`
 
+	MaxTextLength int `json:"max_text_length,omitempty"`
+
 	LocationMessage CapabilitySupportLevel `json:"location_message,omitempty"`
 	Poll            CapabilitySupportLevel `json:"poll,omitempty"`
 	Thread          CapabilitySupportLevel `json:"thread,omitempty"`
@@ -215,6 +217,8 @@ func (rf *RoomFeatures) Hash() []byte {
 	hashMap(hasher, "formatting", rf.Formatting)
 	hashMap(hasher, "file", rf.File)
 
+	hashInt(hasher, "max_text_length", rf.MaxTextLength)
+
 	hashValue(hasher, "location_message", rf.LocationMessage)
 	hashValue(hasher, "poll", rf.Poll)
 	hashValue(hasher, "thread", rf.Thread)