diff --git a/core_info.c b/core_info.c
index b9cde94b77..1d91ecd444 100644
--- a/core_info.c
+++ b/core_info.c
@@ -59,6 +59,8 @@ static void core_info_list_resolve_all_extensions(
             (strlen(core_info_list->list[i].supported_extensions) + 2);
    }
 
+   all_ext_len += strlen("7z|") + strlen("zip|");
+
    if (all_ext_len)
       all_ext = (char*)calloc(1, all_ext_len);
 
@@ -77,10 +79,10 @@ static void core_info_list_resolve_all_extensions(
       strlcat(core_info_list->all_ext, "|", all_ext_len);
    }
 #ifdef HAVE_7ZIP
-   strlcat(core_info_list->all_ext, "7z|", all_ext_len + 3);
+   strlcat(core_info_list->all_ext, "7z|", all_ext_len);
 #endif
 #ifdef HAVE_ZLIB
-   strlcat(core_info_list->all_ext, "zip|", all_ext_len + 4);
+   strlcat(core_info_list->all_ext, "zip|", all_ext_len);
 #endif
 }