diff -Naur asterisk-1.6.2.9-orig/main/dsp.c asterisk-1.6.2.9/main/dsp.c
--- asterisk-1.6.2.9-orig/main/dsp.c	2010-05-19 12:44:06.000000000 -0400
+++ asterisk-1.6.2.9/main/dsp.c	2010-06-05 13:25:49.000000000 -0400
@@ -1424,8 +1424,10 @@
 				}
 				memmove(&dsp->digit_state.digits[0], &dsp->digit_state.digits[1], dsp->digit_state.current_digits);
 				dsp->digit_state.current_digits--;
-				memmove(&dsp->digit_state.digitlen[0], &dsp->digit_state.digitlen[1], dsp->digit_state.current_len * sizeof(dsp->digit_state.digitlen[0]));
-				dsp->digit_state.current_len--;
+				if (dsp->digit_state.current_len > 1) {
+					memmove(&dsp->digit_state.digitlen[0], &dsp->digit_state.digitlen[1], dsp->digit_state.current_len * sizeof(dsp->digit_state.digitlen[0]));
+					dsp->digit_state.current_len--;
+				}
 				dsp->dtmf_began = 0;
 
 				if (dsp->features & DSP_FEATURE_BUSY_DETECT) {