diff --git a/PureGym.Test/TestJson.fs b/PureGym.Test/TestJson.fs
index 0b8df68..1e97558 100644
--- a/PureGym.Test/TestJson.fs
+++ b/PureGym.Test/TestJson.fs
@@ -124,7 +124,7 @@ module TestJson =
                         Latitude = 51.480401
                     }
                 TimeZone = "Europe/London"
-                ReopenDate = "2021-04-12T00:00:00+01 Europe/London"
+                ReopenDate = Some "2021-04-12T00:00:00+01 Europe/London"
             }
 
         [ ovalJson, oval ] |> List.map TestCaseData
diff --git a/PureGym/Dto.fs b/PureGym/Dto.fs
index 175cb97..0ee7a25 100644
--- a/PureGym/Dto.fs
+++ b/PureGym/Dto.fs
@@ -125,7 +125,7 @@ type Gym =
         [<JsonRequired>]
         TimeZone : string
         /// This is a date-time in the format yyyy-MM-ddTHH:mm:ss+01 Europe/London
-        ReopenDate : string
+        ReopenDate : string option
     }
 
     /// Human-readable representation of the most important information about this gym
diff --git a/PureGym/GeneratedDto.fs b/PureGym/GeneratedDto.fs
index 4452ee9..f81c848 100644
--- a/PureGym/GeneratedDto.fs
+++ b/PureGym/GeneratedDto.fs
@@ -232,16 +232,9 @@ module Gym =
     /// Parse from a JSON node.
     let jsonParse (node : System.Text.Json.Nodes.JsonNode) : Gym =
         let ReopenDate =
-            (match node.["reopenDate"] with
-             | null ->
-                 raise (
-                     System.Collections.Generic.KeyNotFoundException (
-                         sprintf "Required key '%s' not found on JSON object" ("reopenDate")
-                     )
-                 )
-             | v -> v)
-                .AsValue()
-                .GetValue<string> ()
+            match node.["reopenDate"] with
+            | null -> None
+            | v -> v.AsValue().GetValue<string> () |> Some
 
         let TimeZone =
             (match node.["timeZone"] with
diff --git a/PureGym/SurfaceBaseline.txt b/PureGym/SurfaceBaseline.txt
index c707f17..5fc5f6f 100644
--- a/PureGym/SurfaceBaseline.txt
+++ b/PureGym/SurfaceBaseline.txt
@@ -39,7 +39,7 @@ PureGym.AuthTokenModule inherit obj
 PureGym.AuthTokenModule.get [static method]: PureGym.UsernamePin -> System.Threading.CancellationToken -> PureGym.AuthToken System.Threading.Tasks.Task
 PureGym.AuthTokenModule.ofBearerToken [static method]: string -> PureGym.AuthToken
 PureGym.Gym inherit obj, implements PureGym.Gym System.IEquatable, System.Collections.IStructuralEquatable, PureGym.Gym System.IComparable, System.IComparable, System.Collections.IStructuralComparable
-PureGym.Gym..ctor [constructor]: (string, int, int, PureGym.GymAddress, string, string, PureGym.GymOpeningHours, PureGym.GymAccessOptions, PureGym.GymLocation, string, string)
+PureGym.Gym..ctor [constructor]: (string, int, int, PureGym.GymAddress, string, string, PureGym.GymOpeningHours, PureGym.GymAccessOptions, PureGym.GymLocation, string, string option)
 PureGym.Gym.AccessOptions [property]: [read-only] PureGym.GymAccessOptions
 PureGym.Gym.Address [property]: [read-only] PureGym.GymAddress
 PureGym.Gym.EmailAddress [property]: [read-only] string
@@ -51,7 +51,7 @@ PureGym.Gym.get_Id [method]: unit -> int
 PureGym.Gym.get_Location [method]: unit -> PureGym.GymLocation
 PureGym.Gym.get_Name [method]: unit -> string
 PureGym.Gym.get_PhoneNumber [method]: unit -> string
-PureGym.Gym.get_ReopenDate [method]: unit -> string
+PureGym.Gym.get_ReopenDate [method]: unit -> string option
 PureGym.Gym.get_Status [method]: unit -> int
 PureGym.Gym.get_TimeZone [method]: unit -> string
 PureGym.Gym.GymOpeningHours [property]: [read-only] PureGym.GymOpeningHours
@@ -59,7 +59,7 @@ PureGym.Gym.Id [property]: [read-only] int
 PureGym.Gym.Location [property]: [read-only] PureGym.GymLocation
 PureGym.Gym.Name [property]: [read-only] string
 PureGym.Gym.PhoneNumber [property]: [read-only] string
-PureGym.Gym.ReopenDate [property]: [read-only] string
+PureGym.Gym.ReopenDate [property]: [read-only] string option
 PureGym.Gym.Status [property]: [read-only] int
 PureGym.Gym.TimeZone [property]: [read-only] string
 PureGym.GymAccessOptions inherit obj, implements PureGym.GymAccessOptions System.IEquatable, System.Collections.IStructuralEquatable, PureGym.GymAccessOptions System.IComparable, System.IComparable, System.Collections.IStructuralComparable
diff --git a/PureGym/version.json b/PureGym/version.json
index d0e7d61..7bf95a3 100644
--- a/PureGym/version.json
+++ b/PureGym/version.json
@@ -1,5 +1,5 @@
 {
-  "version": "4.0",
+  "version": "5.0",
   "publicReleaseRefSpec": [
     "^refs/heads/main$"
   ],