diff --git a/external/untwine/untwine/mingw/dirlist.hpp b/external/untwine/untwine/mingw/dirlist.hpp
index d22668980c1..a70a0ae7b33 100644
--- a/external/untwine/untwine/mingw/dirlist.hpp
+++ b/external/untwine/untwine/mingw/dirlist.hpp
@@ -1 +1,39 @@
-#include "../generic/dirlist.hpp"
+#pragma once
+
+#include <filesystem>
+
+#include <stringconv.hpp>
+
+namespace untwine
+{
+namespace os
+{
+
+// PDAL's directoryList had a bug, so we've imported a working
+// version here so that we can still use older PDAL releases.
+
+inline std::vector<std::string> directoryList(const std::string& dir)
+{
+    namespace fs = std::filesystem;
+
+    std::vector<std::string> files;
+
+    try
+    {
+        fs::directory_iterator it(toNative(dir));
+        fs::directory_iterator end;
+        while (it != end)
+        {
+            files.push_back(fromNative(it->path().string()));
+            it++;
+        }
+    }
+    catch (fs::filesystem_error&)
+    {
+        files.clear();
+    }
+    return files;
+}
+
+} // namespace os
+} // namespace untwine
diff --git a/external/untwine/untwine/mingw/mapfile.h b/external/untwine/untwine/mingw/mapfile.hpp
similarity index 88%
rename from external/untwine/untwine/mingw/mapfile.h
rename to external/untwine/untwine/mingw/mapfile.hpp
index 6d9362643ac..9bf37e9f113 100644
--- a/external/untwine/untwine/mingw/mapfile.h
+++ b/external/untwine/untwine/mingw/mapfile.hpp
@@ -1,6 +1,10 @@
 #pragma once
 
+#include <windows.h>
 #include <io.h>
+#include <fcntl.h>
+
+#include <stringconv.hpp>
 
 namespace untwine
 {
@@ -30,7 +34,7 @@ public:
     HANDLE m_handle;
 };
 
-MapContext mapFile(const std::string& filename, bool readOnly, size_t pos, size_t size)
+inline MapContext mapFile(const std::string& filename, bool readOnly, size_t pos, size_t size)
 {
     MapContext ctx;
 
@@ -61,7 +65,7 @@ MapContext mapFile(const std::string& filename, bool readOnly, size_t pos, size_
     return ctx;
 }
 
-MapContext unmapFile(MapContext ctx)
+inline MapContext unmapFile(MapContext ctx)
 {
     if (UnmapViewOfFile(ctx.m_addr) == 0)
         ctx.m_error = "Couldn't unmap file.";