diff --git a/sysmo-usim-tool.sjs1.py b/sysmo-usim-tool.sjs1.py
index eb8e46c..16d44f5 100755
--- a/sysmo-usim-tool.sjs1.py
+++ b/sysmo-usim-tool.sjs1.py
@@ -54,6 +54,7 @@ def helptext():
 	print "   -s  --seq-parameters ........... Show MILENAGE SEQ/SQN parameters"
 	print "   -S  --reset-seq-parameters...... Reset MILENAGE SEQ/SQN parameters to default"
 	print "   -I, --set-iccid ................ Set ICCID value"
+	print "   -J, --set-imsi ................. Set IMSI value"
 	print ""
 
 
@@ -76,16 +77,18 @@ def main(argv):
 	getopt_write_iccid = None
 	getopt_seq_par = False
 	getopt_reset_seq_par = False
+	getopt_write_imsi = None
 
 	# Analyze commandline options
 	try:
 		opts, args = getopt.getopt(argv,
-			"ha:ucmtT:lL:oO:C:kK:fiI:sS",
+			"ha:ucmtT:lL:oO:C:kK:fiI:sSJ:",
 				["help","adm1=","usim","classic",
 				 "mode","auth","set-auth=","milenage",
 				 "set-milenage","opc","set-op=","set-opc=",
 				 "ki","set-ki=","force","iccid","set-iccid=",
-				 "seq-parameters", "reset-seq-parameters"])
+				 "seq-parameters", "reset-seq-parameters",
+                                 "set-imsi"])
 	except getopt.GetoptError:
 		print " * Error: Invalid commandline options"
 		sys.exit(2)
@@ -133,6 +136,8 @@ def main(argv):
 			getopt_seq_par = True
 		elif opt in ("-S", "--reset-sqe-parameters"):
 			getopt_reset_seq_par = True
+		elif opt in ("-J", "--set-imsi"):
+			getopt_write_imsi = asciihex_to_list(pad_asciihex(arg, True, '9'))
 
 
 	if not getopt_adm1:
@@ -234,6 +239,10 @@ def main(argv):
 		sysmo_usim_reset_milenage_sqn_params(sim)
 		print("")
 
+	if getopt_write_imsi:
+		print "Writing IMSI value..."
+		sysmo_usim_write_imsi(sim, getopt_write_imsi)
+		print("")
 
 	print "Done!"
 
diff --git a/sysmo_usimsjs1.py b/sysmo_usimsjs1.py
index d569b72..09dc249 100644
--- a/sysmo_usimsjs1.py
+++ b/sysmo_usimsjs1.py
@@ -47,7 +47,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #      +--[EF_OPC 0x00F7]
 #      |
 #      +--[EF_KI 0x00FF]
-
+#      |
+#      +--[EF_IMSI 0x6F07]
 
 import sys
 from card import *
@@ -574,3 +575,19 @@ def sysmo_usim_write_iccid(sim, iccid):
 
 	print " * Programming..."
 	sim.update_binary(swap_nibbles(iccid))
+
+
+# Program new IMSI value
+def sysmo_usim_write_imsi(sim, imsi):
+	print " * New ISMI setting:"
+	print "   IMSI: " + hexdump(imsi)
+
+	sysmo_usim_init(sim)
+
+        sim.select(GSM_SIM_DF_GSM)
+	sim.select(GSM_SIM_EF_IMSI)
+
+        imsi = [len(imsi)] + swap_nibbles(imsi)
+
+	print " * Programming..."
+	sim.update_binary(imsi)
diff --git a/utils.py b/utils.py
index b7777e0..f492778 100644
--- a/utils.py
+++ b/utils.py
@@ -51,10 +51,12 @@ def asciihex_to_list(string):
 
 
 # Pad an ascihex string with a nibble in case it is "incomplete"
-def pad_asciihex(string, padding='f'):
+def pad_asciihex(string, front=False, padding='f'):
 
-	if len(string) % 2 != 0:
-		return string + padding
+	if front and len(string) % 2 != 0:
+		return padding + string
+	elif len(string) % 2 != 0:
+                return string + padding
 	return string