diff --git a/CMake/Macros.cmake b/CMake/Macros.cmake
index fcc8f53e91..14b82c309e 100644
--- a/CMake/Macros.cmake
+++ b/CMake/Macros.cmake
@@ -40,6 +40,7 @@ set(CURL_TEST_DEFINES "")  # Initialize global variable
 # Return result in variable: CURL_TEST_OUTPUT
 macro(curl_internal_test _curl_test)
   if(NOT DEFINED "${_curl_test}")
+    string(REPLACE ";" " " _cmake_required_flags "${CMAKE_REQUIRED_FLAGS}")
     string(REPLACE ";" " " _cmake_required_definitions "${CMAKE_REQUIRED_DEFINITIONS}")
     set(_curl_test_add_libraries "")
     if(CMAKE_REQUIRED_LIBRARIES)
@@ -52,7 +53,7 @@ macro(curl_internal_test _curl_test)
       ${PROJECT_BINARY_DIR}
       "${CMAKE_CURRENT_SOURCE_DIR}/CMake/CurlTests.c"
       CMAKE_FLAGS
-        "-DCOMPILE_DEFINITIONS:STRING=-D${_curl_test} ${CURL_TEST_DEFINES} ${_cmake_required_definitions}"
+        "-DCOMPILE_DEFINITIONS:STRING=-D${_curl_test} ${CURL_TEST_DEFINES} ${_cmake_required_flags} ${_cmake_required_definitions}"
         "${_curl_test_add_libraries}"
       OUTPUT_VARIABLE CURL_TEST_OUTPUT)
     if(${_curl_test})
diff --git a/CMake/PickyWarnings.cmake b/CMake/PickyWarnings.cmake
index a41b71ef89..e2af24e4e5 100644
--- a/CMake/PickyWarnings.cmake
+++ b/CMake/PickyWarnings.cmake
@@ -28,8 +28,7 @@ set(_picky "")
 if(CURL_WERROR AND
    ((CMAKE_C_COMPILER_ID STREQUAL "GNU" AND
      NOT DOS AND  # Watt-32 headers use the '#include_next' GCC extension
-     CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 5.0 AND
-     CMAKE_VERSION VERSION_GREATER_EQUAL 3.23.0) OR  # to avoid check_symbol_exists() conflicting with GCC -pedantic-errors
+     CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 5.0) OR
    CMAKE_C_COMPILER_ID MATCHES "Clang"))
   list(APPEND _picky "-pedantic-errors")
 endif()
@@ -45,9 +44,7 @@ if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID MATCHES "Clang")
 endif()
 
 if(MSVC)
-  if(CMAKE_C_FLAGS MATCHES "[/-]W[0-4]")
-    string(REGEX REPLACE "[/-]W[0-4]" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
-  endif()
+  string(REGEX REPLACE "[/-]W[0-4]" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
   list(APPEND _picky "-W4")
 elseif(BORLAND)
   list(APPEND _picky "-w-")  # Disable warnings on Borland to avoid changing 3rd party code.
@@ -294,7 +291,15 @@ if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND MSVC)
 endif()
 
 if(_picky)
-  string(REPLACE ";" " " _picky "${_picky}")
-  string(APPEND CMAKE_C_FLAGS " ${_picky}")
-  message(STATUS "Picky compiler options: ${_picky}")
+  string(REPLACE ";" " " _picky_tmp "${_picky}")
+  message(STATUS "Picky compiler options: ${_picky_tmp}")
+  set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "${_picky}")
+
+  # Apply to all feature checks
+  list(REMOVE_ITEM _picky "-pedantic-errors")  # Must not pass to feature checks
+  string(REPLACE ";" " " _picky_tmp "${_picky}")
+  list(APPEND CMAKE_REQUIRED_FLAGS "${_picky_tmp}")
+
+  unset(_picky)
+  unset(_picky_tmp)
 endif()
diff --git a/CMakeLists.txt b/CMakeLists.txt
index df23fab240..c25d823ef9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -282,7 +282,8 @@ endif()
 include(PickyWarnings)
 
 if(CYGWIN OR CMAKE_SYSTEM_NAME STREQUAL "Linux")
-  string(APPEND CMAKE_C_FLAGS " -D_GNU_SOURCE")  # Required for sendmmsg() and accept4()
+  set_property(DIRECTORY APPEND PROPERTY COMPILE_DEFINITIONS "_GNU_SOURCE")  # Required for accept4(), pipe2(), sendmmsg()
+  list(APPEND CMAKE_REQUIRED_DEFINITIONS "-D_GNU_SOURCE")  # Apply to all feature checks
 endif()
 
 option(ENABLE_DEBUG "Enable curl debug features (for developing curl itself)" OFF)
@@ -360,8 +361,8 @@ if(WIN32)
   if(CURL_STATIC_CRT AND MSVC)
     if(MSVC_VERSION GREATER_EQUAL 1900 OR BUILD_STATIC_CURL OR NOT BUILD_CURL_EXE)
       set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
-      string(APPEND CMAKE_C_FLAGS_RELEASE " -MT")
-      string(APPEND CMAKE_C_FLAGS_DEBUG " -MTd")
+      set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "$<$<CONFIG:Release>:-MT>")
+      set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "$<$<CONFIG:Debug>:-MTd>")
     else()
       message(WARNING "Static CRT requires UCRT, static libcurl or no curl executable.")
     endif()
@@ -2005,14 +2006,14 @@ if(WIN32)
 endif()
 
 if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")  # MSVC but exclude clang-cl
-  string(APPEND CMAKE_C_FLAGS " -MP")  # Parallel compilation
+  set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "-MP")  # Parallel compilation
 endif()
 
 if(CURL_WERROR)
   if(MSVC)
-    string(APPEND CMAKE_C_FLAGS " -WX")
+    set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "-WX")
   else()
-    string(APPEND CMAKE_C_FLAGS " -Werror")  # This assumes clang or gcc style options
+    set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS "-Werror")  # This assumes clang or gcc style options
   endif()
 endif()