diff --git a/include/jtag/register.h b/include/jtag/register.h
index 13f2a743..29de1fdd 100644
--- a/include/jtag/register.h
+++ b/include/jtag/register.h
@@ -35,7 +35,7 @@ tap_register *register_alloc( int len );
 tap_register *register_duplicate( const tap_register *tr );
 void register_free( tap_register *tr );
 tap_register *register_fill( tap_register *tr, int val );
-const char *register_get_string( tap_register *tr );
+const char *register_get_string( const tap_register *tr );
 tap_register *register_init( tap_register *tr, const char *value );
 int register_compare( const tap_register *tr, const tap_register *tr2 );
 int register_match( const tap_register *tr, const char *expr );
diff --git a/jtag/src/tap/register.c b/jtag/src/tap/register.c
index 3896a0fe..eaea4879 100644
--- a/jtag/src/tap/register.c
+++ b/jtag/src/tap/register.c
@@ -87,7 +87,7 @@ register_fill( tap_register *tr, int val )
 }
 
 const char *
-register_get_string( tap_register *tr )
+register_get_string( const tap_register *tr )
 {
 	int i;
 
@@ -149,7 +149,7 @@ int
 register_match( const tap_register *tr, const char *expr )
 {
 	int i;
-	char *s;
+	const char *s;
 
 	if (!tr || !expr || (tr->len != strlen( expr )))
 		return 0;