diff --git a/CMakeLists.txt b/CMakeLists.txt
index a878c7c47..e19d18f1b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,9 +11,12 @@ if (NOT DEFINED PACKAGE_VERSION)
   set(PACKAGE_VERSION "0")
 endif()
 
-set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_CXX_EXTENSIONS OFF)
+if(NOT CMAKE_CXX_STANDARD)
+  set(CMAKE_CXX_STANDARD 17)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
+  set(CMAKE_CXX_EXTENSIONS OFF)
+  message(STATUS "setting C++ standard to C++${CMAKE_CXX_STANDARD}")
+endif()
 
 set(CMAKE_MODULE_PATH
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"