diff --git a/asn1/ranap/RANAP-IEs.asn b/asn1/ranap/RANAP-IEs.asn
index 9593ee8..78fcfbe 100644
--- a/asn1/ranap/RANAP-IEs.asn
+++ b/asn1/ranap/RANAP-IEs.asn
@@ -842,7 +842,7 @@
 	iE-Extensions		IE-Extensions			OPTIONAL
 }
 
-IMSI	::= TBCD-STRING (SIZE (3..8))
+IMSI	::= OCTET STRING (SIZE (3..8))
 -- Reference: 23.003
 
 IncludeVelocity		::= ENUMERATED {