--- a/src/arith-ops.h
+++ b/src/arith-ops.h
@@ -26,7 +26,7 @@
 
 #include "oct-cmplx.h"
 
-#include "tree-expr.h"
+#include "pt-exp.h"
 
 class Matrix;
 class ComplexMatrix;

--- a/src/file-info.h
+++ b/src/file-info.h
@@ -26,12 +26,12 @@
 #if !defined (octave_file_info_h)
 #define octave_file_info_h 1
 
+#include <cstdio>
+
 #include <string>
 
 #include <Pix.h>
 
-#include "oct-obj.h"
-
 class
 file_info
 {

--- a/src/load-save.h
+++ b/src/load-save.h
@@ -24,8 +24,9 @@
 #if !defined (octave_load_save_h)
 #define octave_load_save_h 1
 
+class ostream;
+
 class tree_constant;
-class ostream;
 
 extern int save_ascii_data (ostream& os, const tree_constant& t,
 			    char *name = 0, int strip_nan_and_inf = 0,

--- a/src/oct-obj.h
+++ b/src/oct-obj.h
@@ -29,18 +29,11 @@
 #endif
 
 #include "Array.h"
-#include "mx-base.h"
 
-class tree_constant;
-class Matrix;
-class RowVector;
-class ColumnVector;
-class DiagMatrix;
-class ComplexMatrix;
-class ComplexRowVector;
-class ComplexColumnVector;
-class ComplexDiagMatrix;
-class Range;
+// Including this is all we need because pt-const.h gives us
+// declarations for all the data types Octave knows about.
+
+#include "pt-const.h"
 
 class
 Octave_object : public Array<tree_constant>

--- a/src/pr-output.h
+++ b/src/pr-output.h
@@ -28,10 +28,10 @@
 
 #include "oct-cmplx.h"
 
+class ComplexMatrix;
 class Matrix;
-class ComplexMatrix;
+class Range;
 class charMatrix;
-class Range;
 
 extern void octave_print_internal (ostream& os, double d,
 				   int pr_as_read_syntax = 0);

--- a/src/symtab.h
+++ b/src/symtab.h
@@ -32,8 +32,6 @@
 
 #include "variables.h"
 
-class ostream;
-
 // Must be multiple of 2.
 #define HASH_TABLE_SIZE 1024
 #define HASH_MASK (HASH_TABLE_SIZE - 1)

--- a/src/utils.h
+++ b/src/utils.h
@@ -26,7 +26,7 @@
 
 class istream;
 class ostrstream;
-class tree_constant;
+
 class Octave_object;
 
 extern char *strsave (const char *);

--- a/src/variables.h
+++ b/src/variables.h
@@ -24,18 +24,14 @@
 #if !defined (octave_variables_h)
 #define octave_variables_h 1
 
-class istream;
-class ostrstream;
 class symbol_record;
 class symbol_table;
-class tree;
+
 class tree_fvc;
 class tree_constant;
 class Octave_object;
 
 struct builtin_mapper_function;
-struct builtin_function;
-struct builtin_variable;
 
 typedef int (*sv_Function)(void);