diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8920544..ac0a8ed 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -103,7 +103,9 @@ if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
     set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin" CACHE PATH "Executable/dll output dir.")
 endif()
 
-set(JSONCPP_USE_SECURE_MEMORY "0" CACHE STRING "-D...=1 to use memory-wiping allocator for STL")
+if(JSONCPP_USE_SECURE_MEMORY)
+    add_definitions("-DJSONCPP_USE_SECURE_MEMORY=1")
+endif()
 
 configure_file("${PROJECT_SOURCE_DIR}/version.in"
     "${PROJECT_BINARY_DIR}/version"