--- a/src/ov-base-fixed-mat.h
+++ b/src/ov-base-fixed-mat.h
@@ -38,10 +38,7 @@
 #include <octave/ov-base.h>
 #include <octave/ov-typeinfo.h>
 
-class Octave_map;
 class octave_value_list;
-
-class tree_walker;
 
 template <class MT>
 class