diff --git a/vrclient_x64/gen_wrapper.py b/vrclient_x64/gen_wrapper.py
index 282acde8..c2c94861 100755
--- a/vrclient_x64/gen_wrapper.py
+++ b/vrclient_x64/gen_wrapper.py
@@ -342,6 +342,10 @@ def ivrrendermodels_load_into_texture_d3d11_async(cppname, method):
     assert "005" in cppname or "006" in cppname
     return "ivrrendermodels_load_into_texture_d3d11_async"
 
+def ivrmailbox_undoc3(cppname, method):
+    assert "001" in cppname
+    return "ivrmailbox_undoc3"
+
 method_overrides = [
     ("IVRClientCore", "Init", ivrclientcore_init),
     ("IVRClientCore", "GetGenericInterface", ivrclientcore_get_generic_interface),
@@ -355,6 +359,7 @@ method_overrides = [
     ("IVRRenderModels", "LoadTextureD3D11_Async", ivrrendermodels_load_texture_d3d11_async),
     ("IVRRenderModels", "FreeTextureD3D11", ivrrendermodels_free_texture_d3d11),
     ("IVRRenderModels", "LoadIntoTextureD3D11_Async", ivrrendermodels_load_into_texture_d3d11_async),
+    ("IVRMailbox", "undoc3", ivrmailbox_undoc3),
 ]
 
 method_overrides_data = [
diff --git a/vrclient_x64/vrclient_x64/json_converter.cpp b/vrclient_x64/vrclient_x64/json_converter.cpp
new file mode 100644
index 00000000..076d95b3
--- /dev/null
+++ b/vrclient_x64/vrclient_x64/json_converter.cpp
@@ -0,0 +1,109 @@
+#include <windows.h>
+#include <wine/debug.h>
+
+WINE_DEFAULT_DEBUG_CHANNEL(vrclient);
+
+#include "vrclient_private.h"
+
+#include "json/json.h"
+
+extern "C" {
+
+static bool ends_with(const std::string &s, char c)
+{
+    auto e = s.end();
+    if(e != s.begin()){
+        --e;
+        return *e == c;
+    }
+    return false;
+}
+
+static bool convert_path_to_win(std::string &s)
+{
+    bool need_slash = ends_with(s, '\\') || ends_with(s, '/');
+
+    DWORD sz = MultiByteToWideChar(CP_UTF8, 0, s.c_str(), -1, NULL, 0);
+    if(!sz)
+    {
+        return false;
+    }
+
+    WCHAR *dos_path = (WCHAR *)HeapAlloc(GetProcessHeap(), 0, sz * sizeof(WCHAR));
+    if(!dos_path)
+    {
+        return false;
+    }
+
+    sz = MultiByteToWideChar(CP_UTF8, 0, s.c_str(), -1, dos_path, sz);
+    if(!sz)
+    {
+        HeapFree(GetProcessHeap(), 0, dos_path);
+        return false;
+    }
+
+    char *unix_path = wine_get_unix_file_name(dos_path);
+    if(!unix_path)
+    {
+        HeapFree(GetProcessHeap(), 0, dos_path);
+        return false;
+    }
+
+    /* XXX assuming the system encoding is UTF-8 */
+    s = unix_path;
+
+    if(need_slash)
+        s += '/';
+
+    HeapFree(GetProcessHeap(), 0, unix_path);
+    HeapFree(GetProcessHeap(), 0, dos_path);
+
+    return true;
+}
+
+char *json_convert_paths(const char *input)
+{
+    Json::Reader reader;
+    Json::Value root;
+
+    if(!reader.parse(input, root))
+        return NULL;
+
+    if(root.isMember("type") &&
+            root["type"].isString() &&
+            root["type"] == "set_paths")
+    {
+        if(root.isMember("webroot") &&
+                root["webroot"].isString())
+        {
+            std::string path(root["webroot"].asString());
+            if(convert_path_to_win(path))
+                root["webroot"] = path;
+        }
+
+        if(root.isMember("models") &&
+                root["models"].isString())
+        {
+            std::string path(root["models"].asString());
+            if(convert_path_to_win(path))
+                root["models"] = path;
+        }
+
+        Json::FastWriter writer;
+
+        std::string contents(writer.write(root));
+
+        char *ret = (char *)malloc(contents.length() + 1);
+        if(!ret)
+            return NULL;
+
+        size_t len = contents.copy(ret, contents.length());
+        ret[len] = 0;
+
+        return ret;
+    }
+
+    return NULL;
+}
+
+}
diff --git a/vrclient_x64/vrclient_x64/vrclient_main.c b/vrclient_x64/vrclient_x64/vrclient_main.c
index 79bf03de..ea8e375e 100644
--- a/vrclient_x64/vrclient_x64/vrclient_main.c
+++ b/vrclient_x64/vrclient_x64/vrclient_main.c
@@ -1270,6 +1270,20 @@ EVRRenderModelError ivrrendermodels_load_into_texture_d3d11_async(
     return error;
 }
 
+vrmb_typeb ivrmailbox_undoc3(
+        vrmb_typeb (*cpp_func)(void *, vrmb_typea, const char *, const char *),
+        void *linux_side, vrmb_typea a, const char *b, const char *c, unsigned int version)
+{
+    vrmb_typeb r;
+    char *converted = json_convert_paths(c);
+
+    r = cpp_func(linux_side, a, b, converted ? converted : c);
+
+    free(converted);
+
+    return r;
+}
+
 void destroy_compositor_data(struct compositor_data *data)
 {
     IWineD3D11Device *wined3d_device;
diff --git a/vrclient_x64/vrclient_x64/vrclient_private.h b/vrclient_x64/vrclient_x64/vrclient_private.h
index e7fe066a..e8d82521 100644
--- a/vrclient_x64/vrclient_x64/vrclient_private.h
+++ b/vrclient_x64/vrclient_x64/vrclient_private.h
@@ -6,6 +6,16 @@
 #define VRCLIENT_HAVE_DXVK
 #endif
 
+#if __cplusplus
+extern "C" {
+#endif
+
+char *json_convert_paths(const char *input);
+
+#if __cplusplus
+}
+#endif
+
 /* TODO these should be generated */
 typedef struct __winISteamClient winISteamClient;
 typedef struct __winISteamUser winISteamUser;
diff --git a/vrclient_x64/vrclient_x64/winIVRMailbox.c b/vrclient_x64/vrclient_x64/winIVRMailbox.c
index dae5cff5..f7b65885 100644
--- a/vrclient_x64/vrclient_x64/winIVRMailbox.c
+++ b/vrclient_x64/vrclient_x64/winIVRMailbox.c
@@ -43,7 +43,7 @@ DEFINE_THISCALL_WRAPPER(winIVRMailbox_IVRMailbox_001_undoc3, 20)
 vrmb_typeb __thiscall winIVRMailbox_IVRMailbox_001_undoc3(winIVRMailbox_IVRMailbox_001 *_this, vrmb_typea a, const char * b, const char * c)
 {
     TRACE("%p\n", _this);
-    return cppIVRMailbox_IVRMailbox_001_undoc3(_this->linux_side, a, b, c);
+    return ivrmailbox_undoc3(cppIVRMailbox_IVRMailbox_001_undoc3, _this->linux_side, a, b, c, 1);
 }
 
 DEFINE_THISCALL_WRAPPER(winIVRMailbox_IVRMailbox_001_undoc4, 24)