diff --git a/dll/win32/shell32/shelldesktop/CDirectoryList.cpp b/dll/win32/shell32/shelldesktop/CDirectoryList.cpp
index 2bdd36f0eb..d1084b749f 100644
--- a/dll/win32/shell32/shelldesktop/CDirectoryList.cpp
+++ b/dll/win32/shell32/shelldesktop/CDirectoryList.cpp
@@ -12,6 +12,8 @@ WINE_DEFAULT_DEBUG_CHANNEL(shcn);
 
 BOOL CDirectoryList::ContainsPath(LPCWSTR pszPath) const
 {
+    if (PathIsRelativeW(pszPath))
+        MessageBoxW(NULL, pszPath, L"PathIsRelativeW", MB_ICONERROR);
     assert(!PathIsRelativeW(pszPath));
 
     for (INT i = 0; i < m_items.GetSize(); ++i)