diff --git a/dlls/rpcrt4/rpc_async.c b/dlls/rpcrt4/rpc_async.c
index c57337aa669..4ff86a34a56 100644
--- a/dlls/rpcrt4/rpc_async.c
+++ b/dlls/rpcrt4/rpc_async.c
@@ -32,6 +32,8 @@
 
 WINE_DEFAULT_DEBUG_CHANNEL(rpc);
 
+#define RPC_ASYNC_SIGNATURE 0x43595341
+
 /***********************************************************************
  *           RpcAsyncInitializeHandle [RPCRT4.@]
  *
@@ -48,8 +50,23 @@ WINE_DEFAULT_DEBUG_CHANNEL(rpc);
  */
 RPC_STATUS WINAPI RpcAsyncInitializeHandle(PRPC_ASYNC_STATE pAsync, unsigned int Size)
 {
-    FIXME("(%p, %d): stub\n", pAsync, Size);
-    return RPC_S_INVALID_ASYNC_HANDLE;
+    TRACE("(%p, %d)\n", pAsync, Size);
+
+    if (Size != sizeof(*pAsync))
+    {
+        ERR("invalid Size %d\n", Size);
+        return ERROR_INVALID_PARAMETER;
+    }
+
+    pAsync->Size = sizeof(*pAsync);
+    pAsync->Signature = RPC_ASYNC_SIGNATURE;
+    pAsync->Lock = 0;
+    pAsync->Flags = 0;
+    pAsync->StubInfo = NULL;
+    pAsync->RuntimeInfo = NULL;
+    memset(&pAsync->Reserved, 0, sizeof(*pAsync) - FIELD_OFFSET(RPC_ASYNC_STATE, Reserved));
+
+    return RPC_S_OK;
 }
 
 /***********************************************************************
diff --git a/dlls/rpcrt4/tests/rpc_async.c b/dlls/rpcrt4/tests/rpc_async.c
index 0d32fd1e64a..0cc5557ce06 100644
--- a/dlls/rpcrt4/tests/rpc_async.c
+++ b/dlls/rpcrt4/tests/rpc_async.c
@@ -36,35 +36,25 @@ static void test_RpcAsyncInitializeHandle(void)
     int i;
 
     status = pRpcAsyncInitializeHandle((PRPC_ASYNC_STATE)buffer, sizeof(buffer));
-    todo_wine
     ok(status == ERROR_INVALID_PARAMETER, "RpcAsyncInitializeHandle with large Size should have returned ERROR_INVALID_PARAMETER instead of %ld\n", status);
 
     status = pRpcAsyncInitializeHandle(&async, sizeof(async) - 1);
-    todo_wine
     ok(status == ERROR_INVALID_PARAMETER, "RpcAsyncInitializeHandle with small Size should have returned ERROR_INVALID_PARAMETER instead of %ld\n", status);
 
     memset(&async, 0xcc, sizeof(async));
     status = pRpcAsyncInitializeHandle(&async, sizeof(async));
-    todo_wine
     ok(status == RPC_S_OK, "RpcAsyncInitializeHandle failed with error %ld\n", status);
 
-    todo_wine
     ok(async.Size == sizeof(async), "async.Size wrong: %d\n", async.Size);
-    todo_wine
     ok(async.Signature == 0x43595341, "async.Signature should be 0x43595341, but is 0x%x instead\n", async.Signature);
-    todo_wine
     ok(async.Lock == 0, "async.Lock should be 0, but is %d instead\n", async.Lock);
-    todo_wine
     ok(async.Flags == 0, "async.Flags should be 0, but is %d instead\n", async.Flags);
-    todo_wine
     ok(async.StubInfo == NULL, "async.StubInfo should be NULL, not %p\n", async.StubInfo);
     ok(async.UserInfo == (void *)0xcccccccc, "async.UserInfo should be unset, not %p\n", async.UserInfo);
-    todo_wine
     ok(async.RuntimeInfo == NULL, "async.RuntimeInfo should be NULL, not %p\n", async.RuntimeInfo);
     ok(async.Event == 0xcccccccc, "async.Event should be unset, not %d\n", async.Event);
     ok(async.NotificationType == 0xcccccccc, "async.NotificationType should be unset, not %d\n", async.NotificationType);
     for (i = 0; i < 4; i++)
-        todo_wine
         ok(async.Reserved[i] == 0x0, "async.Reserved[%d] should be 0x0, not 0x%lx\n", i, async.Reserved[i]);
 }
 
@@ -74,7 +64,6 @@ static void test_RpcAsyncGetCallStatus(void)
     RPC_STATUS status;
 
     status = pRpcAsyncInitializeHandle(&async, sizeof(async));
-    todo_wine
     ok(status == RPC_S_OK, "RpcAsyncInitializeHandle failed with error %ld\n", status);
 
     status = pRpcAsyncGetCallStatus(&async);