diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index b935cbf1ae7..3c9a25062f5 100644
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -286,6 +286,11 @@ static bool shouldUseMmap(int FD,
                           bool RequiresNullTerminator,
                           int PageSize,
                           bool IsVolatileSize) {
+#ifdef _WIN32
+    // Do not use mmap on Windows in order to avoid file locking
+    return false;
+#endif
+
   // mmap may leave the buffer without null terminator if the file size changed
   // by the time the last page is mapped in, so avoid it if the file size is
   // likely to change.