diff --git a/CMakeLists.txt b/CMakeLists.txt
index efcfb3a..9d77165 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,13 @@
 cmake_minimum_required(VERSION 3.15)
 project(CloudStreamingArgsDebugger LANGUAGES CXX)
 
+# Use C++20 project-wide. The GitHub Actions build.yml invokes cl with
+# /std:c++20 directly; keep the CMake path in sync so the two build modes
+# compile the same language.
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
 # Specify that this is a Win32 application with wWinMain entry point
 set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /SUBSYSTEM:WINDOWS")
 
diff --git a/path_info.cpp b/path_info.cpp
index 037f6af..024f7a8 100644
--- a/path_info.cpp
+++ b/path_info.cpp
@@ -30,8 +30,6 @@ template <typename Fill> std::wstring FillWithGrowingBuffer(Fill fill)
     for (int attempt = 0; attempt < 6; ++attempt)
     {
         SetLastError(ERROR_SUCCESS);
-        // `&buf[0]` yields `wchar_t*` in both C++17 and C++20; `buf.data()`
-        // would only do so in C++20. Tests compile with C++17.
         DWORD len = fill(&buf[0], static_cast<DWORD>(buf.size()));
         if (len == 0)
             return {};
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 127332b..db11ddc 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -4,9 +4,11 @@ project(ArgumentDebuggerTests LANGUAGES CXX)
 # Explicitly specify that tests are console applications
 set(CMAKE_WIN32_EXECUTABLE OFF)
 
-# Set C++ standard
-set(CMAKE_CXX_STANDARD 17)
+# Set C++ standard (kept in sync with the top-level CMakeLists.txt and with
+# the /std:c++20 flag used by .github/workflows/build.yml).
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
 
 # Find GoogleTest package
 find_package(GTest CONFIG REQUIRED)