diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7f163041f..f7ba4fa38 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,6 +15,12 @@ include(ExternalProject)
 ##
 ## OPTIONS
 ##
+
+if (POLICY CMP0077)
+    # Allow CMake 3.13+ to override options when using FetchContent / add_subdirectory.
+    cmake_policy(SET CMP0077 NEW)
+endif ()
+
 option(JSON_BuildTests "Build the unit tests when BUILD_TESTING is enabled." ON)
 option(JSON_Install "Install CMake targets during install step." ON)
 option(JSON_MultipleHeaders "Use non-amalgamated version of the library." OFF)