diff --git a/lfs/linux b/lfs/linux
index 2865fd7b3..ff8f5e4af 100644
--- a/lfs/linux
+++ b/lfs/linux
@@ -160,6 +160,8 @@ endif
 	cd $(DIR_SRC) && rm -rf mISDN-*
 	cd $(DIR_SRC) && tar xfz $(DIR_DL)/mISDN-1_1_5.tar.gz
 	cd $(DIR_SRC)/mISDN-1_1_5 && yes 'yes' | ./std2kern -k /usr/src/linux
+	
+	cd $(DIR_APP)/drivers/isdn/hardware/mISDN && patch -Np0 < $(DIR_SRC)/src/patches/mISDN-avmfritz.patch
 
 ifeq "$(SMP)" ""
 	# Only do this once on the non-SMP pass
diff --git a/src/patches/mISDN-avmfritz.patch b/src/patches/mISDN-avmfritz.patch
new file mode 100644
index 000000000..69c880f40
--- /dev/null
+++ b/src/patches/mISDN-avmfritz.patch
@@ -0,0 +1,11 @@
+--- avm_fritz.c.old	Tue Feb 13 11:43:45 2007
++++ avm_fritz.c	Wed Apr 11 15:26:32 2007
+@@ -781,6 +781,8 @@
+ 			spin_lock_irqsave(inst->hwlock, flags);
+ 			ret = modehdlc(bch, bch->channel,
+ 				bch->inst.pid.protocol[1]);
++			if (bch->inst.pid.protocol[2] == ISDN_PID_L2_B_TRANS)
++				test_and_set_bit(FLG_L2DATA, &bch->Flags);
+ 			spin_unlock_irqrestore(inst->hwlock, flags);
+ 		}
+ 		skb_trim(skb, 0);