diff --git a/lsteamclient/steamclient_main.c b/lsteamclient/steamclient_main.c
index 321ef745..7959d0d5 100644
--- a/lsteamclient/steamclient_main.c
+++ b/lsteamclient/steamclient_main.c
@@ -1,12 +1,14 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <stdio.h>
-#include <dlfcn.h>
 #include <limits.h>
 #include <stdint.h>
 #include <pthread.h>
 #include <assert.h>
 
+#define __USE_GNU
+#include <dlfcn.h>
+
 #include "windef.h"
 #include "winbase.h"
 #include "winnls.h"
@@ -42,6 +44,37 @@ static pthread_cond_t callback_queue_callback_event;
 static pthread_cond_t callback_queue_ready_event;
 static pthread_cond_t callback_queue_complete_event;
 
+static void * (WINAPI *p_NtCurrentTeb)(void);
+
+static void init_ntdll_so_funcs(void)
+{
+    Dl_info info;
+    UINT64 unix_funcs;
+    unsigned int status;
+    void *ntdll;
+
+    status = NtQueryVirtualMemory(GetCurrentProcess(), GetModuleHandleW(L"ntdll.dll"), (MEMORY_INFORMATION_CLASS)1000 /*MemoryWineUnixFuncs*/,
+            &unix_funcs, sizeof(unix_funcs), NULL);
+    if (status)
+    {
+        fprintf(stderr, "err:lsteamclient:init_ntdll_so_funcs NtQueryVirtualMemory status %#x.\n", status);
+        return;
+    }
+    if (!dladdr((void *)(ULONG_PTR)unix_funcs, &info))
+    {
+        fprintf(stderr, "err:lsteamclient:init_ntdll_so_funcs dladdr failed.\n");
+        return;
+    }
+    ntdll = dlopen(info.dli_fname, RTLD_NOW);
+    if (!ntdll)
+    {
+        fprintf(stderr, "err:lsteamclient:init_ntdll_so_funcs could not find ntdll.so.\n");
+        return;
+    }
+    p_NtCurrentTeb = dlsym(ntdll, "NtCurrentTeb");
+    dlclose(ntdll);
+}
+
 BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, void *reserved)
 {
     TRACE("(%p, %u, %p)\n", instance, reason, reserved);
@@ -51,6 +84,7 @@ BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, void *reserved)
         case DLL_PROCESS_ATTACH:
             DisableThreadLibraryCalls(instance);
             steam_overlay_event = CreateEventA(NULL, TRUE, FALSE, "__wine_steamclient_GameOverlayActivated");
+            init_ntdll_so_funcs();
             break;
         case DLL_PROCESS_DETACH:
             if (callback_thread_handle)
@@ -76,6 +110,13 @@ BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, void *reserved)
     return TRUE;
 }
 
+BOOL is_native_thread(void)
+{
+    if (!p_NtCurrentTeb)
+        return TRUE;
+    return !p_NtCurrentTeb();
+}
+
 void sync_environment(void)
 {
     static const char *steamapi_envs[] =
@@ -743,7 +784,12 @@ static DWORD WINAPI callback_thread(void *dummy)
                         cb_data.steam_api_warning_hook.msg);
                 callback_complete(cookie);
                 break;
-
+            case STEAM_API_CALLBACK_ONE_PARAM:
+                TRACE("STEAM_API_CALLBACK_ONE_PARAM func %p, param %p.\n",
+                        cb_data.func, cb_data.steam_api_callback_one_param.param);
+                ((void (WINAPI *)(void *))cb_data.func)(cb_data.steam_api_callback_one_param.param);
+                callback_complete(cookie);
+                break;
             default:
                 ERR("Unexpected callback type %u.\n", cb_data.type);
                 break;
diff --git a/lsteamclient/steamclient_manual_common.cpp b/lsteamclient/steamclient_manual_common.cpp
index 8368a28d..0ac2a941 100644
--- a/lsteamclient/steamclient_manual_common.cpp
+++ b/lsteamclient/steamclient_manual_common.cpp
@@ -88,13 +88,25 @@ static void __attribute__((ms_abi)) win_Release(struct winSteamNetworkingMessage
 static void lin_FreeData(struct SteamNetworkingMessage_t *lin_msg)
 {
     struct msg_wrapper *msg = msg_wrapper_from_lin(lin_msg);
+    struct callback_data cb_data;
 
-    TRACE("%p\n", msg);
     if (!msg)
         return;
 
-    if(msg->win_msg.m_pfnFreeData)
+    if (!msg->win_msg.m_pfnFreeData)
+        return;
+
+    if (!is_native_thread())
+    {
+        TRACE("msg %p, callback %p.\n", msg, msg->win_msg.m_pfnFreeData);
         ((void (__attribute__((ms_abi))*)(struct winSteamNetworkingMessage_t_153a *))msg->win_msg.m_pfnFreeData)(&msg->win_msg);
+        return;
+    }
+
+    cb_data.type = STEAM_API_CALLBACK_ONE_PARAM;
+    cb_data.func = (void *)msg->win_msg.m_pfnFreeData;
+    cb_data.steam_api_callback_one_param.param = (void *)&msg->win_msg;
+    execute_callback(&cb_data);
 }
 
 void *network_message_lin_to_win_(void *msg_, unsigned int version)
@@ -104,7 +116,7 @@ void *network_message_lin_to_win_(void *msg_, unsigned int version)
 
     msg = (struct msg_wrapper *)HeapAlloc(GetProcessHeap(), 0, sizeof(*msg));
 
-    TRACE("lin_msg %p, msg %p.\n", lin_msg, msg);
+    TRACE("lin_msg %p, msg %p, m_cbSize %d.\n", lin_msg, msg, lin_msg->m_cbSize);
 
     msg->lin_msg = lin_msg;
 
diff --git a/lsteamclient/steamclient_private.h b/lsteamclient/steamclient_private.h
index e383bfcc..072300ab 100644
--- a/lsteamclient/steamclient_private.h
+++ b/lsteamclient/steamclient_private.h
@@ -75,6 +75,7 @@ enum callback_type
 {
     SOCKET_DEBUG_OUTPUT = 1,
     STEAM_API_WARNING_HOOK,
+    STEAM_API_CALLBACK_ONE_PARAM,
 };
 
 struct callback_data
@@ -96,10 +97,16 @@ struct callback_data
             const char *msg;
         }
         steam_api_warning_hook;
+        struct
+        {
+            void *param;
+        }
+        steam_api_callback_one_param;
     };
 };
 
 void execute_callback(struct callback_data *cb_data);
+BOOL is_native_thread(void);
 
 #ifdef __cplusplus
 }