--- a/liboctave/sparse-sort.cc
+++ b/liboctave/sparse-sort.cc
@@ -49,6 +49,8 @@
   return  (i->r < j->r);
 }
 
+template class octave_sort<octave_sparse_sort_idxl *>;
+
 // Need to know the original order of the sorted indexes in
 // sparse assignments, and this class does that
 bool
@@ -58,6 +60,8 @@
   return (i->i < j->i);
 }
 
+template class octave_sort<octave_idx_vector_sort *>;
+
 /*
 ;;; Local Variables: ***
 ;;; mode: C++ ***