GraphQL - Apollo printSchema error: TypeError: Cannot read properties of undefined (reading 'kind')

I am trying to use the printSchema function from Apollo to include @directives in the GQL Schema.

However it keeps showing this error:

TypeError: Cannot read properties of undefined (reading 'kind')
    at KnownDirectivesRule (node_modules\graphql\validation\rules\KnownDirectivesRule.js:43
:13)
    at \node_modules\graphql\validation\validate.js:90:12
    at Array.map (<anonymous>)
    at validateSDL (\node_modules\graphql\validation\validate.js:89:24)
    at buildSchemaFromSDL (\node_modules\@apollo\federation\node_modules\@apollo\subgraph\di
st\schema-helper\buildSchemaFromSDL.js:143:47)
    at Object.buildSubgraphSchema (\node_modules\@apollo\federation\node_modules\@apollo\sub
graph\dist\buildSubgraphSchema.js:26:57)
    at file:///finalizeProcessFunction.js:34:37
    at SchemaBuilder.applyHooks (\node_modules\graphile-build\node8plus\SchemaBuilder.js:264
:20)
    at SchemaBuilder.buildSchema (\node_modules\graphile-build\node8plus\SchemaBuilder.js:34
0:33)
    at SchemaBuilder.watchSchema (\node_modules\graphile-build\node8plus\SchemaBuilder.js:40
8:34)

My schema is very long so I don't paste the whole file here, but basically it's just a normal GQL Schema that has multiple type, then Query, Mutation and Subscription.

The directives that I am adding is under Subscription called @aws_subscribe, it is use for AppSync subscription.

So the code that pops this error is this:

let federatedSchema = printSchema.buildSubgraphSchema(schema);

The schema type is GraphQLSchema and it looks like this:

What am I missing here?

from GraphQL - Apollo printSchema error: TypeError: Cannot read properties of undefined (reading 'kind')