Index: apps/app_mixmonitor.c
===================================================================
--- apps/app_mixmonitor.c	(revision 378188)
+++ apps/app_mixmonitor.c	(working copy)
@@ -509,7 +509,8 @@
 			last_slash = strrchr(filename, '/');
 
 			if ((*ext = strrchr(filename, '.')) && (*ext > last_slash)) {
-				**(ext++) = '\0';
+				**ext = '\0';
+				*ext += 1;
 			} else {
 				*ext = "raw";
 			}