diff --git a/src/{{ project_name_snake }}/export_types.py b/src/{{ project_name_snake }}/export_types.py
index 8c58aad..2749ce1 100644
--- a/src/{{ project_name_snake }}/export_types.py	
+++ b/src/{{ project_name_snake }}/export_types.py	
@@ -49,7 +49,7 @@ def export_types(schema_file: str):
 
 def generate_typescript_interfaces(schema_dir: Path):
     run_command(
-        f"npx -y json-schema-to-typescript@15.0.4 -i '{schema_dir / '*.json'}' -o {schema_dir}"
+        f"npx -y json-schema-to-typescript@15.0.4 -i '{schema_dir / '*.json'}' -o {schema_dir} --additionalProperties=false"
     )
     run_command(f"npx -y prettier@3.5.1 --write {schema_dir}")
 
diff --git a/test-proj/src/test_proj/export_types.py b/test-proj/src/test_proj/export_types.py
index 8c58aad..2749ce1 100644
--- a/test-proj/src/test_proj/export_types.py
+++ b/test-proj/src/test_proj/export_types.py
@@ -49,7 +49,7 @@ def export_types(schema_file: str):
 
 def generate_typescript_interfaces(schema_dir: Path):
     run_command(
-        f"npx -y json-schema-to-typescript@15.0.4 -i '{schema_dir / '*.json'}' -o {schema_dir}"
+        f"npx -y json-schema-to-typescript@15.0.4 -i '{schema_dir / '*.json'}' -o {schema_dir} --additionalProperties=false"
     )
     run_command(f"npx -y prettier@3.5.1 --write {schema_dir}")
 
diff --git a/test-proj/ui/src/schemas/MySchema.d.ts b/test-proj/ui/src/schemas/MySchema.d.ts
index 42a7105..524f880 100644
--- a/test-proj/ui/src/schemas/MySchema.d.ts
+++ b/test-proj/ui/src/schemas/MySchema.d.ts
@@ -9,5 +9,4 @@ export type Hello = string;
 
 export interface MySchema {
   hello: Hello;
-  [k: string]: unknown;
 }
diff --git a/ui/src/schemas/MySchema.d.ts b/ui/src/schemas/MySchema.d.ts
index 42a7105..524f880 100644
--- a/ui/src/schemas/MySchema.d.ts
+++ b/ui/src/schemas/MySchema.d.ts
@@ -9,5 +9,4 @@ export type Hello = string;
 
 export interface MySchema {
   hello: Hello;
-  [k: string]: unknown;
 }