diff --git a/Source/DOH/doh.h b/Source/DOH/doh.h
index 043b979c4..96ed12667 100644
--- a/Source/DOH/doh.h
+++ b/Source/DOH/doh.h
@@ -292,7 +292,7 @@ extern int      DohCopyto(DOHFile *input, DOHFile *output);
  * ----------------------------------------------------------------------------- */
 
 extern DOHList  *DohNewList();
-extern void DohSortList(DOH *lo, int (*cmp)(DOH *, DOH *));
+extern void DohSortList(DOH *lo, int (*cmp)(const DOH *, const DOH *));
 
 /* -----------------------------------------------------------------------------
  * Hash
diff --git a/Source/DOH/list.c b/Source/DOH/list.c
index bd909f596..9c3ab2038 100644
--- a/Source/DOH/list.c
+++ b/Source/DOH/list.c
@@ -361,13 +361,13 @@ DohNewList() {
     return DohObjMalloc(&DohListType,l);
 }
 
-static int (*List_sort_compare_func)(DOH *, DOH *);
+static int (*List_sort_compare_func)(const DOH *, const DOH *);
 static int List_qsort_compare(const void *a, const void *b) {
   return List_sort_compare_func(*((DOH **)a), *((DOH **)b));
 }
 
 /* Sort a list */
-void DohSortList(DOH *lo, int (*cmp)(DOH *, DOH *)) {
+void DohSortList(DOH *lo, int (*cmp)(const DOH *, const DOH *)) {
   List *l = (List *) ObjData(lo);
   if (cmp) {
     List_sort_compare_func = cmp;