diff --git a/extern/acgl/include/ACGL/Utils/MemoryMappedFileWinImpl.hh b/extern/acgl/include/ACGL/Utils/MemoryMappedFileWinImpl.hh
index 93d52eb..b93adc3 100644
--- a/extern/acgl/include/ACGL/Utils/MemoryMappedFileWinImpl.hh
+++ b/extern/acgl/include/ACGL/Utils/MemoryMappedFileWinImpl.hh
@@ -13,7 +13,7 @@
 
 #ifdef _WIN32
 #include "MemoryMappedFile.hh"
-#include <Windows.h>
+#include <windows.h>
 class MemoryMappedFileWinImpl
 {
 
@@ -50,4 +50,4 @@ private:
     HANDLE mFileHandle;
     HANDLE mFileMappingHandle;
 };
-#endif
\ No newline at end of file
+#endif