diff --git a/src/print.c b/src/print.c
index 91b44cb3..4d679e82 100644
--- a/src/print.c
+++ b/src/print.c
@@ -60,9 +60,9 @@ max_length (size_t *width, const char *str)
 `--------------------------------*/
 
 static void
-print_core (FILE *out, state *s)
+print_core (FILE *out, const state *s)
 {
-  item_index *sitems = s->items;
+  const item_index *sitems = s->items;
   size_t snritems = s->nitems;
   /* Output all the items of a state, not only its kernel.  */
   if (report_flag & report_itemsets)
@@ -100,7 +100,7 @@ print_core (FILE *out, state *s)
 `------------------------------------------------------------*/
 
 static void
-print_transitions (state *s, FILE *out, bool display_transitions_p)
+print_transitions (const state *s, FILE *out, bool display_transitions_p)
 {
   transitions *trans = s->transitions;
   size_t width = 0;
@@ -128,7 +128,7 @@ print_transitions (state *s, FILE *out, bool display_transitions_p)
       {
         symbol *sym = symbols[TRANSITION_SYMBOL (trans, i)];
         const char *tag = sym->tag;
-        state *s1 = trans->states[i];
+        const state *s1 = trans->states[i];
 
         fprintf (out, "    %s", tag);
         for (int j = width - mbswidth (tag, 0); j > 0; --j)
@@ -146,7 +146,7 @@ print_transitions (state *s, FILE *out, bool display_transitions_p)
 `--------------------------------------------------------*/
 
 static void
-print_errs (FILE *out, state *s)
+print_errs (FILE *out, const state *s)
 {
   errs *errp = s->errs;
   size_t width = 0;
@@ -208,7 +208,7 @@ print_reduction (FILE *out, size_t width,
 `-------------------------------------------*/
 
 static void
-print_reductions (FILE *out, state *s)
+print_reductions (FILE *out, const state *s)
 {
   reductions *reds = s->reductions;
   if (reds->num == 0)
@@ -324,7 +324,7 @@ print_reductions (FILE *out, state *s)
 `--------------------------------------------------------------*/
 
 static void
-print_actions (FILE *out, state *s)
+print_actions (FILE *out, const state *s)
 {
   /* Print shifts.  */
   print_transitions (s, out, true);
@@ -340,7 +340,7 @@ print_actions (FILE *out, state *s)
 `----------------------------------*/
 
 static void
-print_state (FILE *out, state *s)
+print_state (FILE *out, const state *s)
 {
   fputs ("\n\n", out);
   fprintf (out, _("State %d"), s->number);
diff --git a/src/state.c b/src/state.c
index 8f17a00c..bc45460d 100644
--- a/src/state.c
+++ b/src/state.c
@@ -231,7 +231,7 @@ state_reductions_set (state *s, int num, rule **reds)
 
 
 int
-state_reduction_find (state *s, rule const *r)
+state_reduction_find (state const *s, rule const *r)
 {
   reductions *reds = s->reductions;
   for (int i = 0; i < reds->num; ++i)
@@ -260,7 +260,7 @@ state_errs_set (state *s, int num, symbol **tokens)
 `--------------------------------------------------*/
 
 void
-state_rule_lookahead_tokens_print (state *s, rule const *r, FILE *out)
+state_rule_lookahead_tokens_print (state const *s, rule const *r, FILE *out)
 {
   /* Find the reduction we are handling.  */
   reductions *reds = s->reductions;
@@ -283,7 +283,7 @@ state_rule_lookahead_tokens_print (state *s, rule const *r, FILE *out)
 }
 
 void
-state_rule_lookahead_tokens_print_xml (state *s, rule const *r,
+state_rule_lookahead_tokens_print_xml (state const *s, rule const *r,
                                        FILE *out, int level)
 {
   /* Find the reduction we are handling.  */
@@ -395,7 +395,7 @@ state_hash_insert (state *s)
 `------------------------------------------------------------------*/
 
 state *
-state_hash_lookup (size_t nitems, item_index *core)
+state_hash_lookup (size_t nitems, const item_index *core)
 {
   size_t items_size = nitems * sizeof *core;
   state *probe = xmalloc (offsetof (state, items) + items_size);
diff --git a/src/state.h b/src/state.h
index 4f0cfd10..a274e611 100644
--- a/src/state.h
+++ b/src/state.h
@@ -247,15 +247,15 @@ void state_reductions_set (state *s, int num, rule **reds);
 
 /* The index of the reduction of state S that corresponds to rule R.
    Aborts if there is no reduction of R in S.  */
-int state_reduction_find (state *s, rule const *r);
+int state_reduction_find (state const *s, rule const *r);
 
 /* Set the errs of STATE.  */
 void state_errs_set (state *s, int num, symbol **errors);
 
 /* Print on OUT all the lookahead tokens such that this STATE wants to
    reduce R.  */
-void state_rule_lookahead_tokens_print (state *s, rule const *r, FILE *out);
-void state_rule_lookahead_tokens_print_xml (state *s, rule const *r,
+void state_rule_lookahead_tokens_print (state const *s, rule const *r, FILE *out);
+void state_rule_lookahead_tokens_print_xml (state const *s, rule const *r,
                                             FILE *out, int level);
 
 /* Create/destroy the states hash table.  */
@@ -264,7 +264,7 @@ void state_hash_free (void);
 
 /* Find the state associated to the CORE, and return it.  If it does
    not exist yet, return NULL.  */
-state *state_hash_lookup (size_t core_size, item_index *core);
+state *state_hash_lookup (size_t core_size, const item_index *core);
 
 /* Insert STATE in the state hash table.  */
 void state_hash_insert (state *s);