diff --git a/support/docs/lib/overlay-doc.nix b/support/docs/lib/overlay-doc.nix
index ea6fdd8e..0d917ed0 100644
--- a/support/docs/lib/overlay-doc.nix
+++ b/support/docs/lib/overlay-doc.nix
@@ -38,14 +38,17 @@ let
         then lib.removePrefix "/" (lib.removePrefix (toString prefix) (toString decl))
         else (toNixpkgsRelative decl)
       ;
-      subpath = head (splitString ":" position);
-      lineno = last (splitString ":" position);
       url =
-        if lib.hasPrefix "<nixpkgs" position
+        if position == null || lib.hasPrefix "<nixpkgs" position
         then null
-        else "${sourceLinkPrefix}/${subpath}#L${lineno}"
+        else let
+          subpath = head (splitString ":" position);
+          lineno = last (splitString ":" position);
+        in "${sourceLinkPrefix}/${subpath}#L${lineno}"
       ;
-      position = toRelative drv.meta.position;
+      position = if drv.meta ? "position" 
+                 then toRelative drv.meta.position
+                 else null;
     in
     {
       entry_type = "package";
diff --git a/support/docs/template/package.erb b/support/docs/template/package.erb
index d0e01fc1..5bab0f58 100644
--- a/support/docs/template/package.erb
+++ b/support/docs/template/package.erb
@@ -40,7 +40,7 @@
         <div><%= license["fullName"] %></div>
       </div>
     <% end %>
-    <% if url && url.strip != "" %>
+    <% if position && url && url.strip != "" %>
       <div class="package-data -position">
         <<%= h_package %>>Declared in:</<%= h_package %>>
         <div><a href="<%= url %>"><%= position %></a></div>