diff --git a/src/lib.rs b/src/lib.rs
index 49244353..e3ddc70a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -398,6 +398,11 @@ where
     }
 }
 
+/// Used to default the `bool` fields to `true` during deserialization.
+fn default_true() -> bool {
+    true
+}
+
 #[cfg(test)]
 mod tests {
     use serde_json::{from_str, to_string};
diff --git a/src/room/create.rs b/src/room/create.rs
index 50053588..1180ce48 100644
--- a/src/room/create.rs
+++ b/src/room/create.rs
@@ -1,8 +1,12 @@
 //! Types for the *m.room.create* event.
 
+use std::convert::TryFrom;
+
 use ruma_identifiers::{EventId, RoomId, RoomVersionId, UserId};
 use serde::{Deserialize, Serialize};
 
+use crate::default_true;
+
 state_event! {
     /// This is the first event in a room and cannot be changed. It acts as the root of all other
     /// events.
@@ -16,11 +20,13 @@ pub struct CreateEventContent {
     pub creator: UserId,
     /// Whether or not this room's data should be transferred to other homeservers.
     #[serde(rename = "m.federate")]
-    pub federate: Option<bool>,
+    #[serde(default = "default_true")]
+    pub federate: bool,
     /// The version of the room. Defaults to "1" if the key does not exist.
+    #[serde(default = "default_room_version_id")]
     pub room_version: RoomVersionId,
     /// A reference to the room this room replaces, if the previous room was upgraded.
-    pub predecessor: PreviousRoom,
+    pub predecessor: Option<PreviousRoom>,
 }
 
 /// A reference to an old room replaced during a room version upgrade.
@@ -31,3 +37,8 @@ pub struct PreviousRoom {
     /// The event ID of the last known event in the old room.
     pub event_id: EventId,
 }
+
+/// Used to default the `room_version` field to room version 1.
+fn default_room_version_id() -> RoomVersionId {
+    RoomVersionId::try_from("1").unwrap()
+}
diff --git a/src/room/power_levels.rs b/src/room/power_levels.rs
index 5209b74c..927ea4d0 100644
--- a/src/room/power_levels.rs
+++ b/src/room/power_levels.rs
@@ -67,6 +67,7 @@ pub struct NotificationPowerLevels {
     pub room: u64,
 }
 
+/// Used to default power levels to 50 during deserialization.
 fn default_power_level() -> u64 {
     50
 }
diff --git a/src/room/server_acl.rs b/src/room/server_acl.rs
index e5aa26e0..bcc999c6 100644
--- a/src/room/server_acl.rs
+++ b/src/room/server_acl.rs
@@ -2,6 +2,8 @@
 
 use serde::{Deserialize, Serialize};
 
+use crate::default_true;
+
 state_event! {
     /// An event to indicate which servers are permitted to participate in the room.
     pub struct ServerAclEvent(ServerAclEventContent) {}
@@ -34,11 +36,6 @@ pub struct ServerAclEventContent {
     pub deny: Vec<String>,
 }
 
-/// Used to default the `allow_ip_literals` field to `true` during deserialization.
-fn default_true() -> bool {
-    true
-}
-
 #[cfg(test)]
 mod tests {
     use super::ServerAclEventContent;