diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index 251801b30..7c12559b4 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -3711,6 +3711,42 @@ testcase TC_assignment_codec_amr_h() runs on test_CT {
 	f_vty_amr_start_mode_restore(false);
 }
 
+/* 'amr start-mode auto' should not keep the (unused) 'smod' bits from previous configuration */
+testcase TC_assignment_codec_amr_startmode_cruft() runs on test_CT {
+	var TestHdlrParams pars := f_gen_test_hdlr_pars();
+	var MSC_ConnHdlr vc_conn;
+
+	var RSL_IE_Body mr_conf := {
+		other := {
+			len := 2,
+			payload := '2004'O /* <- expect ICMI=0, smod=00 */
+		}
+	};
+
+	pars.ass_codec_list := valueof(ts_BSSMAP_IE_CodecList({ts_CodecAMR_F}));
+	pars.ass_codec_list.codecElements[0].s0_7 := '00000100'B; /* 5,90k */
+	pars.ass_codec_list.codecElements[0].s8_15 := '01010111'B;
+	pars.expect_mr_conf_ie := mr_conf;
+
+	f_init(1, true);
+	f_sleep(1.0);
+
+	/* First set nonzero start mode bits */
+	f_vty_amr_start_mode_set(true, "4");
+	/* Now set to auto, and expect the startmode bits to be zero in the message, i.e. ensure that osmo-bsc does not
+	 * let the startmode bits stick around and has deterministic MultiRate config for 'start-mode auto'; that is
+	 * ensured by above '2004'O, where 'x0xx'O indicates ICMI = 0, spare = 0, smod = 00. */
+	f_vty_amr_start_mode_set(true, "auto");
+
+	vc_conn := f_start_handler(refers(f_TC_assignment_codec), pars);
+	vc_conn.done;
+	f_shutdown_helper();
+
+	/* Clear the startmode bits to not affect subsequent tests, in case the bits should indeed stick around. */
+	f_vty_amr_start_mode_set(true, "1");
+	f_vty_amr_start_mode_restore(true);
+}
+
 function f_TC_assignment_codec_amr(boolean fr, octetstring mrconf, bitstring s8_s0, bitstring exp_s8_s0,
 	charstring start_mode := "1")
 runs on test_CT {
@@ -8415,6 +8451,7 @@ control {
 		execute( TC_assignment_codec_amr_h_S7() );
 		execute( TC_assignment_codec_amr_f_start_mode_auto() );
 		execute( TC_assignment_codec_amr_h_start_mode_auto() );
+		execute( TC_assignment_codec_amr_startmode_cruft() );
 	}
 
 	execute( TC_assignment_codec_fr_exhausted_req_hr() );