diff --git a/pico/cd/cd_image.c b/pico/cd/cd_image.c
index 07b55ceb..ae2ef0cd 100644
--- a/pico/cd/cd_image.c
+++ b/pico/cd/cd_image.c
@@ -61,6 +61,7 @@ static void to_upper(char *d, const char *s)
     else
       *d = *s;
   }
+  *d = 0;
 }
 
 // cdd.c uses lba - 150