diff --git a/typescript/testdata/catalogue_client.ts b/typescript/testdata/catalogue_client.ts
index 1b4614b..c91e189 100644
--- a/typescript/testdata/catalogue_client.ts
+++ b/typescript/testdata/catalogue_client.ts
@@ -18,7 +18,7 @@ export interface IGroup {
   title: string,
   nodes: Array<IGroup>,
   groups: Array<IGroup>,
-  child?: IGroup,
+  child?: IGroup | null,
   sub: ISubGroup
 }
 
diff --git a/typescript/testdata/catalogue_with_classes.ts b/typescript/testdata/catalogue_with_classes.ts
index adf1c56..49d7da0 100755
--- a/typescript/testdata/catalogue_with_classes.ts
+++ b/typescript/testdata/catalogue_with_classes.ts
@@ -18,7 +18,7 @@ export interface IGroup {
   title: string,
   nodes: Array<IGroup>,
   groups: Array<IGroup>,
-  child?: IGroup,
+  child?: IGroup | null,
   sub: ISubGroup
 }
 
@@ -32,38 +32,38 @@ export class Campaign implements ICampaign {
   static entityName = "campaign";
 
   id: number = 0;
-  groups: Array<IGroup> = null;
+  groups: Array<IGroup> = null!;
 }
 
 export class CatalogueFirstParams implements ICatalogueFirstParams {
   static entityName = "cataloguefirstparams";
 
-  groups: Array<IGroup> = null;
+  groups: Array<IGroup> = null!;
 }
 
 export class CatalogueSecondParams implements ICatalogueSecondParams {
   static entityName = "cataloguesecondparams";
 
-  campaigns: Array<ICampaign> = null;
+  campaigns: Array<ICampaign> = null!;
 }
 
 export class Group implements IGroup {
   static entityName = "group";
 
   id: number = 0;
-  title: string = null;
-  nodes: Array<IGroup> = null;
-  groups: Array<IGroup> = null;
-  child?: IGroup = null;
-  sub: ISubGroup = null;
+  title: string = null!;
+  nodes: Array<IGroup> = null!;
+  groups: Array<IGroup> = null!;
+  child?: IGroup | null = null;
+  sub: ISubGroup = null!;
 }
 
 export class SubGroup implements ISubGroup {
   static entityName = "subgroup";
 
   id: number = 0;
-  title: string = null;
-  nodes: Array<IGroup> = null;
+  title: string = null!;
+  nodes: Array<IGroup> = null!;
 }
 
 export const factory = (send: any) => ({
diff --git a/typescript/testdata/catalogue_with_types_only.ts b/typescript/testdata/catalogue_with_types_only.ts
index 5cdc864..31e6d3e 100755
--- a/typescript/testdata/catalogue_with_types_only.ts
+++ b/typescript/testdata/catalogue_with_types_only.ts
@@ -18,7 +18,7 @@ export interface IGroup {
   title: string,
   nodes: Array<IGroup>,
   groups: Array<IGroup>,
-  child?: IGroup,
+  child?: IGroup | null,
   sub: ISubGroup
 }
 
diff --git a/typescript/typescript_client.go b/typescript/typescript_client.go
index 09cfb61..a16c044 100644
--- a/typescript/typescript_client.go
+++ b/typescript/typescript_client.go
@@ -147,6 +147,10 @@ func (t Type) DefaultTmpl() string {
 		}
 	}
 
+	if result == "null" && !t.Optional {
+		result = "null!"
+	}
+
 	return result
 }
 
@@ -339,6 +343,10 @@ func convertTSType(models *tsModels, interfacesCache map[string]interface{}, in
 		}, typeMapper)
 	}
 
+	if result.Optional {
+		result.Type += " | null"
+	}
+
 	// apply hook
 	if typeMapper != nil {
 		result = typeMapper(in, result)