diff --git a/src/hlr_ussd.c b/src/hlr_ussd.c
index 399bdbc..35b74b6 100644
--- a/src/hlr_ussd.c
+++ b/src/hlr_ussd.c
@@ -379,6 +379,19 @@
 	return 0;
 }
 
+/* This handler just keeps the session idle unless the guard timer expires. */
+static int handle_ussd_test_idle(struct ss_session *ss,
+				 const struct osmo_gsup_message *gsup,
+				 const struct ss_request *req)
+{
+	char buf[GSM0480_USSD_7BIT_STRING_LEN + 1];
+	snprintf(buf, sizeof(buf), "Keeping your session idle, it will expire "
+		 "at most in %u seconds.", g_hlr->ncss_guard_timeout);
+	ss->state = OSMO_GSUP_SESSION_STATE_CONTINUE;
+	ss_tx_to_ms_ussd_7bit(ss, req->invoke_id, buf);
+	return 0;
+}
+
 
 static const struct hlr_iuse hlr_iuses[] = {
 	{
@@ -389,6 +402,10 @@
 		.name = "own-imsi",
 		.handle_ussd = handle_ussd_own_imsi,
 	},
+	{
+		.name = "test-idle",
+		.handle_ussd = handle_ussd_test_idle,
+	},
 };
 
 const struct hlr_iuse *iuse_find(const char *name)
diff --git a/src/hlr_vty.c b/src/hlr_vty.c
index a054cbe..4b91aa9 100644
--- a/src/hlr_vty.c
+++ b/src/hlr_vty.c
@@ -174,10 +174,11 @@
 #define UROUTE_STR "Routing Configuration\n"
 #define PREFIX_STR "Prefix-Matching Route\n" "USSD Prefix\n"
 
-#define INT_CHOICE "(own-msisdn|own-imsi)"
+#define INT_CHOICE "(own-msisdn|own-imsi|test-idle)"
 #define INT_STR "Internal USSD Handler\n" \
 		"Respond with subscribers' own MSISDN\n" \
-		"Respond with subscribers' own IMSI\n"
+		"Respond with subscribers' own IMSI\n" \
+		"Keep the session idle (useful for testing)\n"
 
 #define EXT_STR "External USSD Handler\n" \
 		"Name of External USSD Handler (IPA CCM ID)\n"