diff --git a/sim-applet/src/org/osmocom/IMSIPseudo/IMSIPseudo.java b/sim-applet/src/org/osmocom/IMSIPseudo/IMSIPseudo.java
index d876dca..79e8edb 100755
--- a/sim-applet/src/org/osmocom/IMSIPseudo/IMSIPseudo.java
+++ b/sim-applet/src/org/osmocom/IMSIPseudo/IMSIPseudo.java
@@ -210,6 +210,8 @@
 			mi = MobileIdentity.str2mi(newIMSI_str, MobileIdentity.MI_IMSI, (byte)9);
 			writeIMSI(mi);
 			showMsg(changed);
+			invalidateTMSI((short)SIMView.FID_EF_LOCI);
+			invalidateTMSI((short)SIMView.FID_EF_LOCIGPRS);
 			refreshIMSI();
 		} catch (Exception e) {
 			showError((short)42);
@@ -234,6 +236,14 @@
 		gsmFile.updateBinary((short)0, mi, (short)0, (short)mi.length);
 	}
 
+	private void invalidateTMSI(short fid)
+	{
+		byte[] TMSI = {(byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff};
+		gsmFile.select((short) SIMView.FID_DF_GSM);
+		gsmFile.select(fid);
+		gsmFile.updateBinary((short)0, TMSI, (short)0, (short)TMSI.length);
+	}
+
 	/*
 	 * - command qualifiers for REFRESH,
 	 *   ETSI TS 101 267 / 3GPP TS 11.14 chapter 12.6 "Command details":