diff --git a/library/Osmocom_Types.ttcn b/library/Osmocom_Types.ttcn
index 23f8fd9..3c0137c 100644
--- a/library/Osmocom_Types.ttcn
+++ b/library/Osmocom_Types.ttcn
@@ -51,6 +51,13 @@
 	AF_INET6	('0a'O)
 }
 
+/* like TTCN-3 int2str() but with padding of leading zeroes */
+function f_int2str(integer i, integer total_digits) return charstring {
+	var charstring istr := int2str(i);
+	var charstring padstr := hex2str(int2hex(0, total_digits - lengthof(istr)));
+	return padstr & istr;
+}
+
 /* return random integer 0 <= ret < max. According to ETSI ES 201 873 C.6.1, rnd() returns *less* than 1, so
 	* the returned int will always be ret < max, or ret <= (max-1). */
 function f_rnd_int(integer max) return integer {