1 files changed, 1 insertions, 1 deletions

diff --git a/scripts/metadata_filter.lua b/scripts/metadata_filter.lua
index ef4f44e..5a547ee 100644
--- a/scripts/metadata_filter.lua
+++ b/scripts/metadata_filter.lua
@@ -52,7 +52,7 @@ function resolve_url(site_url, ref_file, target_file)
     local ref_base_dir = path.directory(ref_file)
     local abs = target_file
     local rel = path.make_relative(abs, ref_base_dir, true)
-    local full = (abs[1] == "/" and (site_url .. abs)) or abs
+    local full = (abs:sub(1, 1) == "/" and (site_url .. abs)) or abs
 
     return { abs = abs, rel = rel, full = full }
 end