diff --git a/include/osmocore/gsm_utils.h b/include/osmocore/gsm_utils.h
index 51e9f2e6a..685bc9018 100644
--- a/include/osmocore/gsm_utils.h
+++ b/include/osmocore/gsm_utils.h
@@ -88,7 +88,7 @@ void gsm_fn2gsmtime(struct gsm_time *time, uint32_t fn);
 uint32_t gsm_gsmtime2fn(struct gsm_time *time);
 
 /* GSM TS 03.03 Chapter 2.6 */
-enum gprs_tlli_tyoe {
+enum gprs_tlli_type {
 	TLLI_LOCAL,
 	TLLI_FOREIGN,
 	TLLI_RANDOM,
@@ -99,5 +99,7 @@ enum gprs_tlli_tyoe {
 /* TS 03.03 Chapter 2.6 */
 int gprs_tlli_type(uint32_t tlli);
 
+uint32_t gprs_tmsi2tlli(uint32_t p_tmsi, enum gprs_tlli_type type);
+
 void generate_backtrace();
 #endif
diff --git a/src/gsm_utils.c b/src/gsm_utils.c
index b392fd37c..913946ed1 100644
--- a/src/gsm_utils.c
+++ b/src/gsm_utils.c
@@ -374,3 +374,20 @@ int gprs_tlli_type(uint32_t tlli)
 
 	return TLLI_RESERVED;
 }
+
+uint32_t gprs_tmsi2tlli(uint32_t p_tmsi, enum gprs_tlli_type type)
+{
+	uint32_t tlli;
+	switch (type) {
+	case TLLI_LOCAL:
+		tlli = p_tmsi | 0xc0000000;
+		break;
+	case TLLI_FOREIGN:
+		tlli = (p_tmsi & 0x3fffffff) | 0x80000000;
+		break;
+	default:
+		tlli = 0;
+		break;
+	}
+	return tlli;
+}