diff --git a/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs b/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs
index a0e980d..09ffae1 100644
--- a/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs
+++ b/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs
@@ -233,7 +233,7 @@ type DefinitionCompiler(schema: OpenApiDocument, provideNullable) as this =
 
     and compileBySchema (ns: NamespaceAbstraction) tyName (schemaObj: OpenApiSchema) isRequired registerNew fromByPathCompiler =
         let compileNewObject() =
-            if schemaObj.Properties.Count = 0 then
+            if schemaObj.Properties.Count = 0 && schemaObj.AllOf.Count = 0 then
                 if not <| isNull tyName then
                     ns.MarkTypeAsNameAlias tyName
 
@@ -245,18 +245,37 @@ type DefinitionCompiler(schema: OpenApiDocument, provideNullable) as this =
                 let ty = ProvidedTypeDefinition(tyName, Some typeof<obj>, isErased = false)
                 registerNew(tyName, ty :> Type)
 
+                // Combine composite schemas
+                let schemaObjProperties =
+                    match schemaObj.AllOf.Count > 0 with
+                    | true ->
+                        schemaObj.AllOf
+                        |> Seq.append [ schemaObj ]
+                        |> Seq.collect(fun x -> x.Properties)
+                    | false -> schemaObj.Properties
+
+                let schemaObjRequired =
+                    match schemaObj.AllOf.Count > 0 with
+                    | true ->
+                        schemaObj.AllOf
+                        |> Seq.append [ schemaObj ]
+                        |> Seq.collect(fun x -> x.Required)
+                        |> System.Collections.Generic.HashSet
+                        :> System.Collections.Generic.ISet<string>
+                    | false -> schemaObj.Required
+
                 // Generate fields and properties
                 let members =
                     let generateProperty = generateProperty(UniqueNameGenerator())
 
-                    List.ofSeq schemaObj.Properties
+                    List.ofSeq schemaObjProperties
                     |> List.map(fun p ->
                         let propName, propSchema = p.Key, p.Value
 
                         if String.IsNullOrEmpty(propName) then
                             failwithf $"Property cannot be created with empty name. TypeName:%A{tyName}; SchemaObj:%A{schemaObj}"
 
-                        let isRequired = schemaObj.Required.Contains(propName)
+                        let isRequired = schemaObjRequired.Contains(propName)
 
                         let pTy =
                             compileBySchema ns (ns.ReserveUniqueName tyName (nicePascalName propName)) propSchema isRequired ns.RegisterType false
@@ -279,15 +298,15 @@ type DefinitionCompiler(schema: OpenApiDocument, provideNullable) as this =
                 // Add full-init constructor
                 let ctorParams, fields =
                     let required, optional =
-                        List.zip (List.ofSeq schemaObj.Properties) members
-                        |> List.partition(fun (x, _) -> schemaObj.Required.Contains(x.Key))
+                        List.zip (List.ofSeq schemaObjProperties) members
+                        |> List.partition(fun (x, _) -> schemaObjRequired.Contains(x.Key))
 
                     (required @ optional)
                     |> List.map(fun (x, (f, p)) ->
                         let paramName = niceCamelName p.Name
 
                         let prParam =
-                            if schemaObj.Required.Contains(x.Key) then
+                            if schemaObjRequired.Contains(x.Key) then
                                 ProvidedParameter(paramName, f.FieldType)
                             else
                                 let paramDefaultValue = this.GetDefaultValue f.FieldType
diff --git a/tests/SwaggerProvider.ProviderTests/Schemas/v3/issue255.yaml b/tests/SwaggerProvider.ProviderTests/Schemas/v3/issue255.yaml
new file mode 100644
index 0000000..eb054ed
--- /dev/null
+++ b/tests/SwaggerProvider.ProviderTests/Schemas/v3/issue255.yaml
@@ -0,0 +1,14 @@
+openapi: 3.0.0
+paths:
+  /run:
+    summary: Do nothing.
+components:
+  schemas:
+    Person:
+      title: Person
+      allOf:
+      - type: object
+        properties:
+          first_name:
+            type: string
+            description: "First Name"
diff --git a/tests/SwaggerProvider.Tests/Schema.Parser.Tests.fs b/tests/SwaggerProvider.Tests/Schema.Parser.Tests.fs
index 5867d93..caff84b 100644
--- a/tests/SwaggerProvider.Tests/Schema.Parser.Tests.fs
+++ b/tests/SwaggerProvider.Tests/Schema.Parser.Tests.fs
@@ -33,9 +33,9 @@ module V3 =
             let defCompiler = DefinitionCompiler(schema, false)
             let opCompiler = OperationCompiler(schema, defCompiler, true, false, true)
             opCompiler.CompileProvidedClients(defCompiler.Namespace)
-            ignore <| defCompiler.Namespace.GetProvidedTypes()
+            defCompiler.Namespace.GetProvidedTypes()
         with e when e.Message.IndexOf("not supported yet") >= 0 ->
-            ()
+            List.Empty
 
 let parserTestBody(path: string) =
     task {
@@ -49,7 +49,7 @@ let parserTestBody(path: string) =
             if path.IndexOf("v2") >= 0 then
                 V2.testSchema schemaStr
             else
-                V3.testSchema schemaStr
+                V3.testSchema schemaStr |> ignore
     }
 
 let rootFolder =
@@ -89,6 +89,17 @@ let ``Parse PetStore``() =
         + "/../SwaggerProvider.ProviderTests/Schemas/v2/petstore.json"
     )
 
+[<Fact>]
+let ``Add definition for schema with only allOf properties``() =
+    let definitions =
+        __SOURCE_DIRECTORY__
+        + "/../SwaggerProvider.ProviderTests/Schemas/v3/issue255.yaml"
+        |> File.ReadAllText
+        |> V3.testSchema
+
+    definitions |> shouldHaveLength 1
+    definitions[0].GetDeclaredProperty("FirstName") |> shouldNotEqual null
+
 (*
 [<Tests>]
 let parseJsonSchemaTests =