diff --git a/TODO-RELEASE b/TODO-RELEASE
index d984813..7b225cc 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -9,3 +9,4 @@
 #library	what			description / commit summary line
 gsup		gsup.h				the 'osmo_gsup_message' struct extended with
 						session information => ABI changed
+						SS/USSD information => ABI changed
diff --git a/include/osmocom/gsm/gsup.h b/include/osmocom/gsm/gsup.h
index 5f45699..dd27493 100644
--- a/include/osmocom/gsm/gsup.h
+++ b/include/osmocom/gsm/gsup.h
@@ -85,6 +85,9 @@
 
 	OSMO_GSUP_SESSION_ID_IE			= 0x30,
 	OSMO_GSUP_SESSION_STATE_IE		= 0x31,
+
+	/*! Supplementary Services payload */
+	OSMO_GSUP_SS_INFO_IE			= 0x35,
 };
 
 /*! GSUP message type */
@@ -114,6 +117,10 @@
 	OSMO_GSUP_MSGT_LOCATION_CANCEL_REQUEST	= 0b00011100,
 	OSMO_GSUP_MSGT_LOCATION_CANCEL_ERROR	= 0b00011101,
 	OSMO_GSUP_MSGT_LOCATION_CANCEL_RESULT	= 0b00011110,
+
+	OSMO_GSUP_MSGT_PROC_SS_REQUEST		= 0b00100000,
+	OSMO_GSUP_MSGT_PROC_SS_ERROR		= 0b00100001,
+	OSMO_GSUP_MSGT_PROC_SS_RESULT		= 0b00100010,
 };
 
 #define OSMO_GSUP_IS_MSGT_REQUEST(msgt) (((msgt) & 0b00000011) == 0b00)
@@ -197,6 +204,10 @@
 	/*! Unique session identifier and origination flag.
          * Encoded only when \ref session_state != 0x00 */
 	uint32_t			session_id;
+
+	/*! ASN.1 encoded MAP payload for Supplementary Services */
+	uint8_t				*ss_info;
+	size_t				ss_info_len;
 };
 
 int osmo_gsup_decode(const uint8_t *data, size_t data_len,
diff --git a/src/gsm/gsup.c b/src/gsm/gsup.c
index 8663f44..b4b60b2 100644
--- a/src/gsm/gsup.c
+++ b/src/gsm/gsup.c
@@ -62,6 +62,11 @@
 	OSMO_VALUE_STRING(OSMO_GSUP_MSGT_LOCATION_CANCEL_REQUEST),
 	OSMO_VALUE_STRING(OSMO_GSUP_MSGT_LOCATION_CANCEL_ERROR),
 	OSMO_VALUE_STRING(OSMO_GSUP_MSGT_LOCATION_CANCEL_RESULT),
+
+	OSMO_VALUE_STRING(OSMO_GSUP_MSGT_PROC_SS_REQUEST),
+	OSMO_VALUE_STRING(OSMO_GSUP_MSGT_PROC_SS_ERROR),
+	OSMO_VALUE_STRING(OSMO_GSUP_MSGT_PROC_SS_RESULT),
+
 	{ 0, NULL }
 };
 
@@ -393,6 +398,11 @@
 			gsup_msg->session_state = *value;
 			break;
 
+		case OSMO_GSUP_SS_INFO_IE:
+			gsup_msg->ss_info = value;
+			gsup_msg->ss_info_len = value_len;
+			break;
+
 		default:
 			LOGP(DLGSUP, LOGL_NOTICE,
 			     "GSUP IE type %d unknown\n", iei);
@@ -580,6 +590,11 @@
 		msgb_tlv_put(msg, OSMO_GSUP_SESSION_STATE_IE, sizeof(u8), &u8);
 	}
 
+	if (gsup_msg->ss_info) {
+		msgb_tlv_put(msg, OSMO_GSUP_SS_INFO_IE,
+				gsup_msg->ss_info_len, gsup_msg->ss_info);
+	}
+
 	return 0;
 }
 
diff --git a/tests/gsup/gsup_test.c b/tests/gsup/gsup_test.c
index 6ead7d2..9712d77 100644
--- a/tests/gsup/gsup_test.c
+++ b/tests/gsup/gsup_test.c
@@ -180,6 +180,43 @@
 		0x31, 0x01, 0x01,
 	};
 
+	static const uint8_t send_ussd_req[] = {
+		0x20, /* OSMO_GSUP_MSGT_PROC_SS_REQUEST */
+		TEST_IMSI_IE,
+
+		/* Session ID and state */
+		0x30, 0x04, 0xde, 0xad, 0xbe, 0xef,
+		0x31, 0x01, 0x01,
+
+		/* SS/USSD information IE */
+		0x35, 0x14,
+			/* ASN.1 encoded MAP payload */
+			0xa1, 0x12,
+				0x02, 0x01, /* Component: invoke */
+				0x01, /* invokeID = 1 */
+				/* opCode: processUnstructuredSS-Request */
+				0x02, 0x01, 0x3b, 0x30, 0x0a, 0x04, 0x01, 0x0f,
+				0x04, 0x05, 0xaa, 0x18, 0x0c, 0x36, 0x02,
+	};
+
+	static const uint8_t send_ussd_res[] = {
+		0x22, /* OSMO_GSUP_MSGT_PROC_SS_RESULT */
+		TEST_IMSI_IE,
+
+		/* Session ID and state */
+		0x30, 0x04, 0xde, 0xad, 0xbe, 0xef,
+		0x31, 0x01, 0x03,
+
+		/* SS/USSD information IE */
+		0x35, 0x08,
+			/* ASN.1 encoded MAP payload */
+			0xa3, 0x06,
+				0x02, 0x01, /* Component: returnError */
+				0x01, /* invokeID = 1 */
+				/* localValue: unknownAlphabet */
+				0x02, 0x01, 0x47,
+	};
+
 	static const struct test {
 		char *name;
 		const uint8_t *data;
@@ -215,6 +252,10 @@
 			send_auth_info_req_auts, sizeof(send_auth_info_req_auts)},
 		{"Dummy message with session IEs",
 			dummy_session_ies, sizeof(dummy_session_ies)},
+		{"SS/USSD processUnstructuredSS-Request / Invoke",
+			send_ussd_req, sizeof(send_ussd_req)},
+		{"SS/USSD processUnstructuredSS-Request / ReturnResult",
+			send_ussd_res, sizeof(send_ussd_res)},
 	};
 
 	printf("Test GSUP message decoding/encoding\n");
@@ -278,7 +319,11 @@
 					osmo_hexdump(t->data + j, ie_end - j));
 
 				OSMO_ASSERT(j <= ie_end - 2);
-				OSMO_ASSERT(t->data[j+0] <= OSMO_GSUP_SESSION_STATE_IE);
+				/**
+				 * FIXME: share the maximal IE value somehow
+				 * in order to avoid manual updating of this
+				 */
+				OSMO_ASSERT(t->data[j+0] <= OSMO_GSUP_SS_INFO_IE);
 				OSMO_ASSERT(t->data[j+1] <= ie_end - j - 2);
 
 				ie_end = j;
diff --git a/tests/gsup/gsup_test.err b/tests/gsup/gsup_test.err
index 5c010e6..ac71ac2 100644
--- a/tests/gsup/gsup_test.err
+++ b/tests/gsup/gsup_test.err
@@ -43,6 +43,12 @@
   generated message: 2b 01 08 21 43 65 87 09 21 43 f5 30 04 de ad be ef 31 01 01 
   original message:  2b 01 08 21 43 65 87 09 21 43 f5 30 04 de ad be ef 31 01 01 
   IMSI:              123456789012345
+  generated message: 20 01 08 21 43 65 87 09 21 43 f5 30 04 de ad be ef 31 01 01 35 14 a1 12 02 01 01 02 01 3b 30 0a 04 01 0f 04 05 aa 18 0c 36 02 
+  original message:  20 01 08 21 43 65 87 09 21 43 f5 30 04 de ad be ef 31 01 01 35 14 a1 12 02 01 01 02 01 3b 30 0a 04 01 0f 04 05 aa 18 0c 36 02 
+  IMSI:              123456789012345
+  generated message: 22 01 08 21 43 65 87 09 21 43 f5 30 04 de ad be ef 31 01 03 35 08 a3 06 02 01 01 02 01 47 
+  original message:  22 01 08 21 43 65 87 09 21 43 f5 30 04 de ad be ef 31 01 03 35 08 a3 06 02 01 01 02 01 47 
+  IMSI:              123456789012345
   message 0: tested 11 truncations, 11 parse failures
   message 1: tested 14 truncations, 13 parse failures
   message 2: tested 83 truncations, 81 parse failures
@@ -58,6 +64,8 @@
   message 12: tested 211 truncations, 209 parse failures
   message 13: tested 45 truncations, 43 parse failures
   message 14: tested 20 truncations, 18 parse failures
+  message 15: tested 42 truncations, 39 parse failures
+  message 16: tested 30 truncations, 27 parse failures
 DLGSUP Stopping DLGSUP logging
   message 0: tested 2816 modifications, 510 parse failures
   message 1: tested 3584 modifications, 768 parse failures
@@ -74,3 +82,5 @@
   message 12: tested 54016 modifications, 4622 parse failures
   message 13: tested 11520 modifications, 1026 parse failures
   message 14: tested 5120 modifications, 1026 parse failures
+  message 15: tested 10752 modifications, 1256 parse failures
+  message 16: tested 7680 modifications, 1265 parse failures
diff --git a/tests/gsup/gsup_test.ok b/tests/gsup/gsup_test.ok
index 1f59902..d63dd2d 100644
--- a/tests/gsup/gsup_test.ok
+++ b/tests/gsup/gsup_test.ok
@@ -29,4 +29,8 @@
           Send Authentication Info Request with AUTS and RAND (UMTS) OK
   Testing Dummy message with session IEs
           Dummy message with session IEs OK
+  Testing SS/USSD processUnstructuredSS-Request / Invoke
+          SS/USSD processUnstructuredSS-Request / Invoke OK
+  Testing SS/USSD processUnstructuredSS-Request / ReturnResult
+          SS/USSD processUnstructuredSS-Request / ReturnResult OK
 Done.