diff --git a/CMakeLists.txt b/CMakeLists.txt
index e89f3f9..ac129c6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.9)
 
 project(fast_float VERSION 0.1.0 LANGUAGES CXX)
 set(CMAKE_CXX_STANDARD 17)