diff --git a/drivers/isdn/mISDN/dsp.h b/drivers/isdn/mISDN/dsp.h
index ded9480..98a33c58f 100644
--- a/drivers/isdn/mISDN/dsp.h
+++ b/drivers/isdn/mISDN/dsp.h
@@ -15,6 +15,7 @@
 #define DEBUG_DSP_TONE		0x0020
 #define DEBUG_DSP_BLOWFISH	0x0040
 #define DEBUG_DSP_DELAY		0x0100
+#define DEBUG_DSP_CLOCK		0x0200
 #define DEBUG_DSP_DTMFCOEFF	0x8000 /* heavy output */
 
 /* options may be: