diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index 6bea49e..dac86ca 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -3351,6 +3351,22 @@
 	vc_conn.done;
 	f_shutdown_helper();
 }
+/* OS#4975: verify that A5/1 is preferred over A5/2 */
+testcase TC_ciph_mode_a5_2_1() runs on test_CT {
+	var MSC_ConnHdlr vc_conn;
+	var TestHdlrParams pars := f_gen_test_hdlr_pars();
+
+	pars.encr := valueof(t_EncrParams('06'O, f_rnd_octstring(8))); /* A5/1 and A5/2 (0x02|0x04)*/
+	pars.encr_exp_enc_alg := '02'O; /* A5/1 */
+
+	f_init(1, true);
+	f_vty_encryption_a5("1 2");
+	f_sleep(1.0);
+	vc_conn := f_start_handler(refers(f_tc_ciph_mode_a5), pars);
+	vc_conn.done;
+	f_vty_encryption_a5_reset();
+	f_shutdown_helper();
+}
 testcase TC_ciph_mode_a5_3() runs on test_CT {
 	var MSC_ConnHdlr vc_conn;
 	var TestHdlrParams pars := f_gen_test_hdlr_pars();
@@ -9228,6 +9244,7 @@
 	execute( TC_assignment_fr_a5_not_sup() );
 	execute( TC_ciph_mode_a5_0() );
 	execute( TC_ciph_mode_a5_1() );
+	execute( TC_ciph_mode_a5_2_1() );
 	execute( TC_ciph_mode_a5_3() );
 	execute( TC_ciph_mode_a5_4() );
 
diff --git a/bsc/MSC_ConnectionHandler.ttcn b/bsc/MSC_ConnectionHandler.ttcn
index 94ec2b9..fc12307 100644
--- a/bsc/MSC_ConnectionHandler.ttcn
+++ b/bsc/MSC_ConnectionHandler.ttcn
@@ -581,6 +581,7 @@
 	RSL_IE_Body	expect_mr_conf_ie optional, /* typically present for AMR codecs */
 	bitstring	expect_mr_s0_s7 optional, /* typically present for AMR codecs */
 	TestHdlrEncrParams encr optional,
+	OCT1		encr_exp_enc_alg optional, /* if set, expect a different enc_alg than encr.enc_alg */
 	TestHdlrParamsLcls lcls,
 	SCCP_PAR_Address sccp_addr_msc optional,
 	SCCP_PAR_Address sccp_addr_bsc optional,
@@ -610,6 +611,7 @@
 	expect_mr_conf_ie := omit,
 	expect_mr_s0_s7 := omit,
 	encr := omit,
+	encr_exp_enc_alg := omit,
 	lcls := {
 		gcr := omit,
 		cfg := omit,
@@ -713,6 +715,19 @@
 	}
 }
 
+function f_cipher_mode_bssmap_to_rsl_exp_enc_alg() runs on MSC_ConnHdlr return RSL_AlgId
+{
+	var OCT1 enc_alg;
+
+	if (ispresent(g_pars.encr_exp_enc_alg)) {
+		enc_alg := g_pars.encr_exp_enc_alg;
+	} else {
+		enc_alg := g_pars.encr.enc_alg;
+	}
+
+	return f_cipher_mode_bssmap_to_rsl(enc_alg);
+}
+
 function f_verify_encr_info(RSL_Message rsl) runs on MSC_ConnHdlr {
 	var RSL_IE_Body encr_info;
 	var RSL_AlgId alg_rsl;
@@ -731,7 +746,7 @@
 
 	/* RSL uses a different representation of the encryption algorithm,
 	 * so we need to convert first */
-	alg_rsl := f_cipher_mode_bssmap_to_rsl(g_pars.encr.enc_alg);
+	alg_rsl := f_cipher_mode_bssmap_to_rsl_exp_enc_alg();
 
 	if (alg_rsl == RSL_ALG_ID_A5_4 and ispresent(g_pars.encr.enc_kc128)) {
 		expect_kc := g_pars.encr.enc_kc128;
@@ -797,7 +812,7 @@
 			Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Unexpected Cipher Mode Complete");
 		} else {
 			setverdict(pass);
-			var RSL_AlgId alg_rsl := f_cipher_mode_bssmap_to_rsl(g_pars.encr.enc_alg);
+			var RSL_AlgId alg_rsl := f_cipher_mode_bssmap_to_rsl_exp_enc_alg();
 			if (oct2int(bssap.pdu.bssmap.cipherModeComplete.chosenEncryptionAlgorithm.algorithmIdentifier) != enum2int(alg_rsl)) {
 				setverdict(fail, "Unexpected Encryption Algorithm ID in BSSMAP Cipher Mode Complete");
 			}
@@ -897,7 +912,7 @@
 		if (not f_rsl_find_ie(chan_act, RSL_IE_ENCR_INFO, encr_info)) {
 			Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Missing Encryption IE in CHAN ACT");
 		} else {
-			var RSL_AlgId alg := f_cipher_mode_bssmap_to_rsl(g_pars.encr.enc_alg);
+			var RSL_AlgId alg := f_cipher_mode_bssmap_to_rsl_exp_enc_alg();
 			var octetstring expect_key;
 			if (alg == RSL_ALG_ID_A5_4) {
 				expect_key := g_pars.encr.enc_kc128;
diff --git a/bsc/expected-results.xml b/bsc/expected-results.xml
index d2052b8..793ca03 100644
--- a/bsc/expected-results.xml
+++ b/bsc/expected-results.xml
@@ -54,6 +54,7 @@
   <testcase classname='BSC_Tests' name='TC_assignment_fr_a5_not_sup' time='MASKED'/>
   <testcase classname='BSC_Tests' name='TC_ciph_mode_a5_0' time='MASKED'/>
   <testcase classname='BSC_Tests' name='TC_ciph_mode_a5_1' time='MASKED'/>
+  <testcase classname='BSC_Tests' name='TC_ciph_mode_a5_2_1' time='MASKED'/>
   <testcase classname='BSC_Tests' name='TC_ciph_mode_a5_3' time='MASKED'/>
   <testcase classname='BSC_Tests' name='TC_ciph_mode_a5_4' time='MASKED'/>
   <testcase classname='BSC_Tests' name='TC_assignment_codec_fr' time='MASKED'/>