diff --git a/source/SOURCE.md b/source/SOURCE.md
index df2e0bf..d6d0068 100644
--- a/source/SOURCE.md
+++ b/source/SOURCE.md
@@ -18,10 +18,6 @@ You will need
 git clone git@github.com:w3c/voiceinteraction.git
 ```
 
-### Download certificates
-
-Download cacert.pem from [curl.haxx.se](https://curl.haxx.se/docs/caextract.html) and place it in the folder `source/w3cipa/w3cipachatgptipaprovider`.
-
 ### Project Structure
 
 The source code is in the folder source/w3cipa
diff --git a/source/w3cipa/w3cipachatgptipaprovider/CMakeLists.txt b/source/w3cipa/w3cipachatgptipaprovider/CMakeLists.txt
index 48f9d60..c1529c0 100644
--- a/source/w3cipa/w3cipachatgptipaprovider/CMakeLists.txt
+++ b/source/w3cipa/w3cipachatgptipaprovider/CMakeLists.txt
@@ -1,16 +1,4 @@
-#
-# IPA Reference Implementation: https://github.com/w3c/voiceinteraction
-#
-# Copyright (C) 2024 World Wide Web Consortium. All Rights Reserved.
-#
-# This work is distributed under the W3C Software and Document License [1]
-# in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
-# the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-#
-# [1] https://www.w3.org/Consortium/Legal/copyright-software
-#
-
-cmake_minimum_required(VERSION 3.22)
+cmake_minimum_required(VERSION 3.22)
 
 project(w3cipachatgptipaprovider LANGUAGES CXX)
 
@@ -43,18 +31,24 @@ target_link_libraries(${PROJECT_NAME} w3cipareferenceimplementation)
 target_link_libraries(${PROJECT_NAME} w3cipaframework)
 target_include_directories(${PROJECT_NAME} PUBLIC include)
 
-#
+# Download cacert.pem if it doesn't exist
+set(CACERT_URL "https://curl.se/ca/cacert.pem")
+set(CACERT_FILE "${CMAKE_CURRENT_SOURCE_DIR}/cacert.pem")
+
+if(NOT EXISTS ${CACERT_FILE})
+    message(STATUS "Downloading cacert.pem from ${CACERT_URL}")
+    file(DOWNLOAD ${CACERT_URL} ${CACERT_FILE} SHOW_PROGRESS)
+endif()
+
 # Add configuration files
-#
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/ChatGPTIPAProvider.json
     ${PROJECT_CONFIG_DIR}/ChatGPTIPAProvider.json COPYONLY)
-configure_file(${CMAKE_CURRENT_SOURCE_DIR}/cacert.pem
+configure_file(${CACERT_FILE}
     ${PROJECT_CONFIG_DIR}/cacert.pem COPYONLY)
 
-#
 # Installation
-#
 install(TARGETS ${PROJECT_NAME} LIBRARY DESTINATION lib)
 install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/ChatGPTIPAProvider.json DESTINATION config)
+install(FILES ${CACERT_FILE} DESTINATION config)
 install(TARGETS ${PROJECT_NAME} FILE_SET HEADERS)
 install(DIRECTORY doc/ DESTINATION doc)
diff --git a/source/w3cipa/w3cipachatgptipaprovider/src/w3c/voiceinteraction/ipa/reference/external/ipa/chatgpt/ChatGPTIPAProvider.cpp b/source/w3cipa/w3cipachatgptipaprovider/src/w3c/voiceinteraction/ipa/reference/external/ipa/chatgpt/ChatGPTIPAProvider.cpp
index 1d49d19..6b961ec 100644
--- a/source/w3cipa/w3cipachatgptipaprovider/src/w3c/voiceinteraction/ipa/reference/external/ipa/chatgpt/ChatGPTIPAProvider.cpp
+++ b/source/w3cipa/w3cipachatgptipaprovider/src/w3c/voiceinteraction/ipa/reference/external/ipa/chatgpt/ChatGPTIPAProvider.cpp
@@ -11,6 +11,7 @@
  */
 
 #include <filesystem>
+#include <fstream>
 
 #include <curl/curl.h>
 #include <log4cplus/loggingmacros.h>