Index: main/cdr.c
===================================================================
--- main/cdr.c	(revision 191560)
+++ main/cdr.c	(working copy)
@@ -945,8 +945,13 @@
 	struct ast_cdr *cdr = chan->cdr;
 
 	for ( ; cdr ; cdr = cdr->next) {
-		if (!ast_test_flag(cdr, AST_CDR_FLAG_LOCKED)) 
+		if (!ast_test_flag(cdr, AST_CDR_FLAG_LOCKED)) {
+			ast_debug(1, "Setting userfield to '%s'\n", userfield);
+			ast_backtrace();
 			ast_copy_string(cdr->userfield, userfield, sizeof(cdr->userfield));
+		} else {
+			ast_debug(1, "Not altering userfield, because CDR is locked.\n");
+		}
 	}
 
 	return 0;