diff --git a/libavcodec/opt.c b/libavcodec/opt.c
index ed7aaa0f86..cfff0c19d9 100644
--- a/libavcodec/opt.c
+++ b/libavcodec/opt.c
@@ -139,6 +139,8 @@ const AVOption *av_set_string(void *obj, const char *name, const char *val){
                 else if(!strcmp(buf, "default")) d= o->default_val;
                 else if(!strcmp(buf, "max"    )) d= o->max;
                 else if(!strcmp(buf, "min"    )) d= o->min;
+                else if(!strcmp(buf, "none"   )) d= 0;
+                else if(!strcmp(buf, "all"    )) d= ~0;
                 else {
                     if (!error)
                         av_log(NULL, AV_LOG_ERROR, "Unable to parse option value \"%s\": %s\n", val, error);