diff --git a/jtag/src/tap/register.c b/jtag/src/tap/register.c
index 28c1db97..f8d3e97a 100644
--- a/jtag/src/tap/register.c
+++ b/jtag/src/tap/register.c
@@ -45,6 +45,8 @@ register_alloc( int len )
 		return NULL;
 	}
 
+	memset(tr->data, 0, len);
+
 	tr->string = malloc( len + 1 );
 	if (!tr->string) {
 		free( tr->data );