diff --git a/CMakeLists.txt b/CMakeLists.txt
index 819c36f..64deb1b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,6 +6,10 @@ else()
   project(json11 VERSION 1.0.0 LANGUAGES CXX)
 endif()
 
+if(NOT CMAKE_DEBUG_POSTFIX)
+  set(CMAKE_DEBUG_POSTFIX d)
+endif()
+
 enable_testing()
 
 option(JSON11_BUILD_TESTS "Build unit tests" OFF)