diff --git a/pySim/cards.py b/pySim/cards.py
index a341b717..cb42d83f 100644
--- a/pySim/cards.py
+++ b/pySim/cards.py
@@ -582,9 +582,9 @@ class SysmoUSIMSJS1(Card):
 		data, sw = self._scc.update_binary('00FF', p['ki'])
 
 		# set OPc in proprietary file
-		content = "01" + p['opc']
-		data, sw = self._scc.update_binary('00F7', content)
-
+		if 'opc' in p:
+			content = "01" + p['opc']
+			data, sw = self._scc.update_binary('00F7', content)
 
 		# write EF.IMSI
 		data, sw = self._scc.update_binary('6f07', enc_imsi(p['imsi']))