diff --git a/CMakeLists.txt b/CMakeLists.txt
index e73079d..beae05e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,6 +8,10 @@ file(GLOB_RECURSE SRC_FILES "src/*.cpp" "src/*.hpp")
 add_library(Arbutils SHARED ${SRC_FILES})
 set_target_properties(Arbutils PROPERTIES LINKER_LANGUAGE CXX)
 
+if (WINDOWS)
+    ADD_DEFINITIONS(-D WINDOWS=1)
+endif (WINDOWS)
+
 file(GLOB_RECURSE TEST_FILES "tests/*.cpp" "tests/*.hpp")
 if (NOT DEFINED CONAN_EXPORTED)
     add_executable(ArbutilsTests ${TEST_FILES} extern/catch.hpp)