diff --git a/pkgs/build-support/fetchurl/default.nix b/pkgs/build-support/fetchurl/default.nix
index b9a640563e36..5ffb70e3a9f8 100644
--- a/pkgs/build-support/fetchurl/default.nix
+++ b/pkgs/build-support/fetchurl/default.nix
@@ -239,7 +239,7 @@ lib.extendMkDerivation {
     derivationArgs
     // {
       name =
-        if pname != null && version != null then
+        if finalAttrs.pname or null != null && finalAttrs.version or null != null then
           "${finalAttrs.pname}-${finalAttrs.version}"
         else if showURLs then
           "urls"