diff --git a/lib/spec/openapi/utils.js b/lib/spec/openapi/utils.js
index b076e2b8..83d611fc 100644
--- a/lib/spec/openapi/utils.js
+++ b/lib/spec/openapi/utils.js
@@ -115,36 +115,6 @@ function resolveServerUrls (servers) {
   return resolvedUrls
 }
 
-function transformDefsToComponents (jsonSchema) {
-  if (typeof jsonSchema === 'object' && jsonSchema !== null) {
-    // Handle patternProperties, that is not part of OpenAPI definitions
-    if (jsonSchema.patternProperties) {
-      jsonSchema.additionalProperties = Object.values(jsonSchema.patternProperties)[0]
-      delete jsonSchema.patternProperties
-    } else if (jsonSchema.const !== undefined) {
-      // OAS 3.1 supports `const` but it is not supported by `swagger-ui`
-      // https://swagger.io/docs/specification/data-models/keywords/
-      jsonSchema.enum = [jsonSchema.const]
-      delete jsonSchema.const
-    }
-
-    Object.keys(jsonSchema).forEach(function (key) {
-      if (key === 'properties') {
-        Object.keys(jsonSchema[key]).forEach(function (prop) {
-          jsonSchema[key][prop] = transformDefsToComponents(jsonSchema[key][prop])
-        })
-      } else if (key === '$ref') {
-        jsonSchema[key] = jsonSchema[key].replace('definitions', 'components/schemas')
-      } else if (key === '$id' || key === '$schema') {
-        delete jsonSchema[key]
-      } else {
-        jsonSchema[key] = transformDefsToComponents(jsonSchema[key])
-      }
-    })
-  }
-  return jsonSchema
-}
-
 function convertExamplesArrayToObject (examples) {
   return examples.reduce((examplesObject, example, index) => {
     if (typeof example === 'object') {
@@ -160,7 +130,7 @@ function convertExamplesArrayToObject (examples) {
 // For supported keys read:
 // https://swagger.io/docs/specification/describing-parameters/
 function plainJsonObjectToOpenapi3 (container, jsonSchema, externalSchemas, securityIgnores = []) {
-  const obj = transformDefsToComponents(resolveLocalRef(jsonSchema, externalSchemas))
+  const obj = convertJsonSchemaToOpenapi3(resolveLocalRef(jsonSchema, externalSchemas))
   let toOpenapiProp
   switch (container) {
     case 'cookie':
@@ -292,7 +262,7 @@ function schemaToMediaRecursive (schema) {
 }
 
 function resolveBodyParams (body, schema, consumes, ref) {
-  const resolved = transformDefsToComponents(ref.resolve(schema))
+  const resolved = convertJsonSchemaToOpenapi3(ref.resolve(schema))
   if ((Array.isArray(consumes) && consumes.length === 0) || consumes === undefined) {
     consumes = ['application/json']
   }
@@ -313,7 +283,7 @@ function resolveBodyParams (body, schema, consumes, ref) {
 
 function resolveCommonParams (container, parameters, schema, ref, sharedSchemas, securityIgnores) {
   const schemasPath = '#/components/schemas/'
-  let resolved = transformDefsToComponents(ref.resolve(schema))
+  let resolved = convertJsonSchemaToOpenapi3(ref.resolve(schema))
 
   // if the resolved definition is in global schema
   if (resolved.$ref && resolved.$ref.startsWith(schemasPath)) {
@@ -339,7 +309,7 @@ function resolveResponse (fastifyResponseJson, produces, ref) {
 
   statusCodes.forEach(statusCode => {
     const rawJsonSchema = fastifyResponseJson[statusCode]
-    const resolved = transformDefsToComponents(ref.resolve(rawJsonSchema))
+    const resolved = convertJsonSchemaToOpenapi3(ref.resolve(rawJsonSchema))
 
     /**
      * 2xx require to be all upper-case
@@ -465,23 +435,80 @@ function prepareOpenapiMethod (schema, ref, openapiObject, url) {
   return openapiMethod
 }
 
-function prepareOpenapiSchemas (schemas, ref) {
-  return Object.entries(schemas)
-    .reduce((res, [name, schema]) => {
-      const _ = { ...schema }
-      const resolved = transformDefsToComponents(ref.resolve(_, { externalSchemas: [schemas] }))
-      resolveSchemaExamplesRecursive(resolved)
-
-      // Swagger doesn't accept $id on /definitions schemas.
-      // The $ids are needed by Ref() to check the URI so we need
-      // to remove them at the end of the process
-      // definitions are added by resolve but they are replace by components.schemas
-      delete resolved.$id
-      delete resolved.definitions
-
-      res[name] = resolved
-      return res
-    }, {})
+function convertJsonSchemaToOpenapi3 (jsonSchema) {
+  if (typeof jsonSchema !== 'object' || jsonSchema === null) {
+    return jsonSchema
+  }
+
+  if (Array.isArray(jsonSchema)) {
+    return jsonSchema.map(convertJsonSchemaToOpenapi3)
+  }
+
+  const openapiSchema = { ...jsonSchema }
+
+  for (const key of Object.keys(openapiSchema)) {
+    const value = openapiSchema[key]
+
+    if (key === '$id' || key === '$schema' || key === 'definitions') {
+      // TODO: this breaks references to the definition properties
+      delete openapiSchema[key]
+      continue
+    }
+
+    if (key === '$ref') {
+      openapiSchema.$ref = value.replace('definitions', 'components/schemas')
+      continue
+    }
+
+    if (key === 'const') {
+      // OAS 3.1 supports `const` but it is not supported by `swagger-ui`
+      // https://swagger.io/docs/specification/data-models/keywords/
+      // TODO: check if enum property already exists
+      // TODO: this breaks references to the const property
+      openapiSchema.enum = [openapiSchema.const]
+      delete openapiSchema.const
+      continue
+    }
+
+    if (key === 'patternProperties') {
+      // TODO: check if additionalProperties property already exists
+      // TODO: this breaks references to the additionalProperties properties
+      // TODO: patternProperties actually allowed in the openapi schema, but should
+      // always start with "x-" prefix
+      openapiSchema.additionalProperties = Object.values(openapiSchema.patternProperties)[0]
+      delete openapiSchema.patternProperties
+      continue
+    }
+
+    if (key === 'properties') {
+      openapiSchema[key] = {}
+      for (const propertyName of Object.keys(value)) {
+        const propertyJsonSchema = value[propertyName]
+        const propertyOpenapiSchema = convertJsonSchemaToOpenapi3(propertyJsonSchema)
+        openapiSchema[key][propertyName] = propertyOpenapiSchema
+      }
+      continue
+    }
+
+    openapiSchema[key] = convertJsonSchemaToOpenapi3(value)
+  }
+
+  return openapiSchema
+}
+
+function prepareOpenapiSchemas (jsonSchemas, ref) {
+  const openapiSchemas = {}
+
+  for (const schemaName of Object.keys(jsonSchemas)) {
+    const jsonSchema = { ...jsonSchemas[schemaName] }
+
+    const resolvedJsonSchema = ref.resolve(jsonSchema, { externalSchemas: [jsonSchemas] })
+    const openapiSchema = convertJsonSchemaToOpenapi3(resolvedJsonSchema)
+    resolveSchemaExamplesRecursive(openapiSchema)
+
+    openapiSchemas[schemaName] = openapiSchema
+  }
+  return openapiSchemas
 }
 
 module.exports = {