diff --git a/include/spdlog/details/os.h b/include/spdlog/details/os.h
index 1d895420..75cc5887 100644
--- a/include/spdlog/details/os.h
+++ b/include/spdlog/details/os.h
@@ -31,7 +31,7 @@
 # ifndef WIN32_LEAN_AND_MEAN
 #  define WIN32_LEAN_AND_MEAN
 # endif
-# include <Windows.h>
+# include <windows.h>
 
 #ifdef __MINGW32__
 #include <share.h>