diff --git a/libclamav/c++/bytecode2llvm.cpp b/libclamav/c++/bytecode2llvm.cpp
index 35d8e9169..804458ea8 100644
--- a/libclamav/c++/bytecode2llvm.cpp
+++ b/libclamav/c++/bytecode2llvm.cpp
@@ -295,8 +295,12 @@ static void rtlib_bzero(void *s, size_t n)
 }
 
 #ifdef _WIN32
+#ifdef _WIN64
+extern "C" void __chkstk(void);
+#else
 extern "C" void _chkstk(void);
 #endif
+#endif
 // Resolve integer libcalls, but nothing else.
 static void* noUnknownFunctions(const std::string& name) {
     void *addr =