diff --git a/reactos/ntoskrnl/include/internal/ntoskrnl.h b/reactos/ntoskrnl/include/internal/ntoskrnl.h
index fb92bffe5b8..7f15784f329 100644
--- a/reactos/ntoskrnl/include/internal/ntoskrnl.h
+++ b/reactos/ntoskrnl/include/internal/ntoskrnl.h
@@ -188,6 +188,7 @@ ProbeAndCaptureUnicodeString(OUT PUNICODE_STRING Dest,
 
                     /* Set it as the buffer */
                     Dest->Buffer = Buffer;
+                    Dest->MaximumLength = Dest->Length + sizeof(WCHAR);
                 }
                 else
                 {