diff --git a/channels/chan_vpb.cc b/channels/chan_vpb.cc
index 0f050a8377..da02ff3e88 100644
--- a/channels/chan_vpb.cc
+++ b/channels/chan_vpb.cc
@@ -1785,7 +1785,7 @@ static int vpb_digit_end(struct ast_channel *ast, char digit, unsigned int durat
 	ast_verb(4, "%s: vpb_digit: asked to play digit[%s]\n", p->dev, s);
 
 	ast_mutex_lock(&p->play_dtmf_lock);
-	strncat(p->play_dtmf, s, sizeof(*p->play_dtmf) - strlen(p->play_dtmf) - 1);
+	strncat(p->play_dtmf, s, sizeof(p->play_dtmf) - strlen(p->play_dtmf) - 1);
 	ast_mutex_unlock(&p->play_dtmf_lock);
 
 	ast_mutex_unlock(&p->lock);