diff --git a/.gitignore b/.gitignore
index f63a763..aeea740 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,8 +2,7 @@
 *~
 # Typescript
 # emitted code
-build/*
-!build/package.json
+build
 
 # ---> Node
 # Logs
diff --git a/build/package.json b/build/package.json
deleted file mode 100644
index 3dbc1ca..0000000
--- a/build/package.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "type": "module"
-}
diff --git a/package.json5 b/package.json5
index 68400a2..959a089 100644
--- a/package.json5
+++ b/package.json5
@@ -20,12 +20,12 @@
    },
    dependencies: {
       'reflect-metadata': '0.1.13',
+      'typescript-rtti': '0.8.3',
    },
    devDependencies: {
       '@types/node': '18.11.18',
       'ts-node': '10.9.1',
       ttypescript: '1.5.15',
       typescript: '4.7.4',
-      'typescript-rtti': '0.8.3',
    },
 }
diff --git a/src/index.ts b/src/index.ts
index 5d8c0e7..13c39fa 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,10 +1,11 @@
+import 'reflect-metadata'
+
 import {Dispatcher} from './core/Dispatcher.js'
 import * as Specifications from './all.js'
 import {Complex} from './Complex/type.js'
 import {absquare as absquare_complex} from './Complex/arithmetic.js'
 
-import 'reflect-metadata'
-import { ReflectedFunctionParameter, ReflectedObjectRef, reflect } from 'typescript-rtti'
+import { CallSite, ReflectedObjectRef, reflect } from 'typescript-rtti'
 import { square } from './generic/arithmetic.js'
 
 // verify that typescript-rtti works (just as experiment)
@@ -21,29 +22,55 @@ console.log()
 //   returnType class Number
 
 // try out a very simple case (just as experiment)
-function createSquare(deps: { 
-   multiply: (a: number, b: number) => number, 
-   subtract: (a: number, b: number) => number 
+function createSquare(deps: {
+   multiply: (a: number, b: number) => number,
+   subtract: (a: number, b: number) => number
 }) {
    return (a: number) => deps.multiply(a, a)
 }
 console.log('reflect createSquare')
 console.log('parameter names', reflect(createSquare).parameters.map(parameter => parameter.name))
-console.log('parameter[0]', (reflect(createSquare).parameters[0] as ReflectedFunctionParameter))
+// console.log('parameter[0]', (reflect(createSquare).parameters[0] as ReflectedFunctionParameter))
 // @ts-ignore
 console.log('parameterTypes[0]', (reflect(createSquare).parameterTypes[0] as ReflectedObjectRef)._ref.m)
-console.log('parameterTypes[0][0]', 
+console.log('parameterTypes[0].ref.m[0]',
    // @ts-ignore
    (reflect(createSquare).parameterTypes[0] as ReflectedObjectRef)._ref.m[0].n,
    // @ts-ignore
    (reflect(createSquare).parameterTypes[0] as ReflectedObjectRef)._ref.m[0]
 )
+console.log('parameterTypes[0].ref.m[0].t.m',
+    // @ts-ignore
+    (reflect(createSquare).parameterTypes[0] as ReflectedObjectRef)._ref.m[0].t.m
+)
 // @ts-ignore
-console.log('parameters[0]', reflect(createSquare).parameters[0])
+// console.log('parameters[0]', reflect(createSquare).parameters[0])
 // FIXME: where to find the information of the types of the dependencies multiply and subtract?
 
+// Test whether we loose the type information when casting to a generic interface
+// Conclusion: we keep the information, that is good.
+console.log()
+console.log('reflect createFunction')
+type MathjsDependencies = Record<string, Function>
+type MathjsCreateFunction = (deps: MathjsDependencies) => Function
+const createFunction: MathjsCreateFunction = createSquare as MathjsCreateFunction
+console.log('parameter names', reflect(createFunction).parameters.map(parameter => parameter.name))
+// @ts-ignore
+console.log('parameterTypes[0]', (reflect(createFunction).parameterTypes[0] as ReflectedObjectRef)._ref.m)
 
 
+
+console.log()
+console.log('CallSite')
+function foo<T>(call? : CallSite) {
+    console.log(reflect(call).typeParameters[0].isClass(String))
+}
+
+function bar<T>(call? : CallSite) {
+    foo<T>();
+}
+bar<String>();
+
 // FIXME: get all types out of Specifications
 // console.log('Specifications', reflect(Specifications)) // Throws errors
 
diff --git a/tsconfig.json b/tsconfig.json
index 4470b45..c761525 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -7,6 +7,7 @@
         "allowJs": false,
         "noImplicitAny": false,
         "moduleResolution": "Node",
+        "module": "commonjs",
         "plugins": [
           {
             "transform": "typescript-rtti/dist/transformer"