diff --git a/dlls/uxtheme/system.c b/dlls/uxtheme/system.c
index 49742c947a0..33e407fdf82 100644
--- a/dlls/uxtheme/system.c
+++ b/dlls/uxtheme/system.c
@@ -690,6 +690,10 @@ HRESULT WINAPI SetWindowTheme(HWND hwnd, LPCWSTR pszSubAppName,
     HRESULT hr;
     TRACE("(%p,%s,%s)\n", hwnd, debugstr_w(pszSubAppName),
           debugstr_w(pszSubIdList));
+
+    if (!hwnd)
+        return E_HANDLE;
+
     hr = UXTHEME_SetWindowProperty(hwnd, atSubAppName, pszSubAppName);
     if(SUCCEEDED(hr))
         hr = UXTHEME_SetWindowProperty(hwnd, atSubIdList, pszSubIdList);
diff --git a/dlls/uxtheme/tests/system.c b/dlls/uxtheme/tests/system.c
index 7ec72e30259..869dbe2cdc9 100644
--- a/dlls/uxtheme/tests/system.c
+++ b/dlls/uxtheme/tests/system.c
@@ -104,7 +104,6 @@ static void test_SetWindowTheme(void)
     HWND    hWnd;
 
     hRes = SetWindowTheme(NULL, NULL, NULL);
-todo_wine
     ok( hRes == E_HANDLE, "Expected E_HANDLE, got 0x%08x\n", hRes);
 
     /* Only do the bare minimum to get a valid hwnd */