diff --git a/CMakeLists.txt b/CMakeLists.txt
index fd09517..36e7507 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,6 +2,9 @@ cmake_minimum_required(VERSION 3.15.0)
 
 project(KnapsackSolver LANGUAGES CXX)
 
+# Avoid FetchContent warning.
+cmake_policy(SET CMP0135 NEW)
+
 # Require C++11.
 set(CMAKE_CXX_STANDARD 11)
 
diff --git a/extern/CMakeLists.txt b/extern/CMakeLists.txt
index 8888333..4005e3c 100644
--- a/extern/CMakeLists.txt
+++ b/extern/CMakeLists.txt
@@ -4,12 +4,9 @@ include(FetchContent)
 # Fetch boost.
 set(BOOST_INCLUDE_LIBRARIES thread filesystem system program_options)
 set(BOOST_ENABLE_CMAKE ON)
-include(FetchContent)
 FetchContent_Declare(
     Boost
-    GIT_REPOSITORY https://github.com/boostorg/boost.git
-    GIT_TAG boost-1.84.0
-    GIT_SHALLOW TRUE
+    URL https://github.com/boostorg/boost/releases/download/boost-1.84.0/boost-1.84.0.tar.xz
     EXCLUDE_FROM_ALL)
 FetchContent_MakeAvailable(Boost)
 
@@ -17,7 +14,7 @@ FetchContent_MakeAvailable(Boost)
 FetchContent_Declare(
     optimizationtools
     GIT_REPOSITORY https://github.com/fontanf/optimizationtools.git
-    GIT_TAG 33a3966ece149d390ec7ce08699669b5267e64aa
+    GIT_TAG 66f61a3e02c746c57584a5d5257e1b1455d4a9ae
     #SOURCE_DIR "${PROJECT_SOURCE_DIR}/../optimizationtools/"
     EXCLUDE_FROM_ALL)
 FetchContent_MakeAvailable(optimizationtools)