diff --git a/include/comedi.h b/include/comedi.h
index 6430aaa..8ebb5eb 100644
--- a/include/comedi.h
+++ b/include/comedi.h
@@ -60,6 +60,7 @@ typedef unsigned short sampl_t;
 #define CR_ALT_FILTER	(1<<26)
 #define CR_DITHER		CR_ALT_FILTER
 #define CR_DEGLITCH		CR_ALT_FILTER
+#define CR_ALT_SOURCE	(1<<27)
 #define CR_INVERT	(1<<31)
 
 #define AREF_GROUND	0x00		/* analog ref = analog ground */
@@ -210,6 +211,7 @@ typedef unsigned short sampl_t;
 //#define INSN_CONFIG_WAVEFORM		0x11
 //#define INSN_CONFIG_TRIG		0x12
 //#define INSN_CONFIG_COUNTER		0x13
+#define INSN_CONFIG_ALT_SOURCE		0x14
 
 /* ioctls */