diff --git a/src/dll/util.c b/src/dll/util.c
index 8ac7f784..2fee90e9 100644
--- a/src/dll/util.c
+++ b/src/dll/util.c
@@ -127,6 +127,11 @@ HANDLE FspCreateDirectoryFileW(
     Length = GetFullPathNameW(FileName, Length + 1, FullFileName, &FilePart);
     if (0 == Length)
         goto exit;
+    if (0 == FilePart)
+    {
+        SetLastError(ERROR_INVALID_NAME);
+        goto exit;
+    }
 
     FilePartChar = *FilePart;
     *FilePart = L'\0';