diff --git a/libs/openzap/src/include/libteletone.h b/libs/openzap/src/include/libteletone.h
index 4029facce8..6e806cec4f 100644
--- a/libs/openzap/src/include/libteletone.h
+++ b/libs/openzap/src/include/libteletone.h
@@ -78,7 +78,7 @@ extern "C" {
 #include <math.h>
 
 #define	TELETONE_MAX_DTMF_DIGITS 128
-#define TELETONE_MAX_TONES 6
+#define TELETONE_MAX_TONES 18
 #define TELETONE_TONE_RANGE 127
 
 typedef double teletone_process_t;