diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index 2029882..066826e 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -2558,7 +2558,7 @@ gen_trace_for_return_address (CORE_ADDR scope, struct gdbarch *gdbarch)
 struct agent_expr *
 gen_printf (CORE_ADDR scope, struct gdbarch *gdbarch,
 	    CORE_ADDR function, LONGEST channel,
-	    char *format, int fmtlen,
+	    const char *format, int fmtlen,
 	    struct format_piece *frags,
 	    int nargs, struct expression **exprs)
 {
diff --git a/gdb/ax-gdb.h b/gdb/ax-gdb.h
index e74d107..04772b7 100644
--- a/gdb/ax-gdb.h
+++ b/gdb/ax-gdb.h
@@ -117,7 +117,7 @@ extern void require_rvalue (struct agent_expr *ax, struct axs_value *value);
 
 struct format_piece;
 extern struct agent_expr *gen_printf (CORE_ADDR, struct gdbarch *,
-				      CORE_ADDR, LONGEST, char *, int,
+				      CORE_ADDR, LONGEST, const char *, int,
 				      struct format_piece *,
 				      int, struct expression **);
 
diff --git a/gdb/ax-general.c b/gdb/ax-general.c
index 32a47a7..8bd4df6 100644
--- a/gdb/ax-general.c
+++ b/gdb/ax-general.c
@@ -337,7 +337,7 @@ ax_tsv (struct agent_expr *x, enum agent_op op, int num)
    is counted in the length.)  */
 
 void
-ax_string (struct agent_expr *x, char *str, int slen)
+ax_string (struct agent_expr *x, const char *str, int slen)
 {
   int i;
 
diff --git a/gdb/ax.h b/gdb/ax.h
index 1c36125..32887ef 100644
--- a/gdb/ax.h
+++ b/gdb/ax.h
@@ -221,7 +221,7 @@ extern void ax_reg_mask (struct agent_expr *ax, int reg);
 extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num);
 
 /* Append a string to the bytecode stream.  */
-extern void ax_string (struct agent_expr *x, char *str, int slen);
+extern void ax_string (struct agent_expr *x, const char *str, int slen);
 
 
 /* Functions for printing out expressions, and otherwise debugging