diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9ae444c..4cde7e2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -28,7 +28,7 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=native -Wall -Wextra")
 elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-    add_definitions(_CRT_SECURE_NO_WARNINGS)
+    add_definitions(-D_CRT_SECURE_NO_WARNINGS=1)
 endif()
 
 #add extra search paths for libraries and includes
diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index 2856e6b..6463212 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -19,7 +19,7 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror -Wall -Wextra -Weffc++ -Wswitch-default")
 elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-    add_definitions(_CRT_SECURE_NO_WARNINGS)
+    add_definitions(-D_CRT_SECURE_NO_WARNINGS=1)
 endif()
 
 foreach (example ${EXAMPLES})
diff --git a/test/unittest/CMakeLists.txt b/test/unittest/CMakeLists.txt
index 3e9752d..5e4a3e9 100644
--- a/test/unittest/CMakeLists.txt
+++ b/test/unittest/CMakeLists.txt
@@ -18,7 +18,7 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror -Weffc++ -Wswitch-default")
 elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-    add_definitions(_CRT_SECURE_NO_WARNINGS)
+    add_definitions(-D_CRT_SECURE_NO_WARNINGS=1)
 endif()
 
 add_library(namespacetest STATIC namespacetest.cpp)