diff --git a/modules/modperl/CString.i b/modules/modperl/CString.i
index 68135a49..9a1fcbb9 100644
--- a/modules/modperl/CString.i
+++ b/modules/modperl/CString.i
@@ -1,3 +1,7 @@
+/*
+   SWIG-generated sources are used here.
+   */
+
 
 %{
 #include <string>