diff --git a/Driver/clang.cpp b/Driver/clang.cpp
index 5e102b9..28659dd 100644
--- a/Driver/clang.cpp
+++ b/Driver/clang.cpp
@@ -622,6 +622,8 @@
   
   // Handle isysroot.
   if (Group == System) {
+    // FIXME: Portability.  This should be a sys::Path interface, this doesn't
+    // handle things like C:\ right, nor win32 \\network\device\blah.
     if (isysroot.size() != 1 || isysroot[0] != '/') // Add isysroot if present.
       MappedPath.append(isysroot.begin(), isysroot.end());
     if (Path[0] != '/')  // If in the system group, add a /.