diff --git a/pkgs/build-support/fetchgitlab/default.nix b/pkgs/build-support/fetchgitlab/default.nix
index 7ac209654967d..8a2b0ffa31d6b 100644
--- a/pkgs/build-support/fetchgitlab/default.nix
+++ b/pkgs/build-support/fetchgitlab/default.nix
@@ -94,7 +94,7 @@ lib.makeOverridable (
               cat > private-token <<EOF
               PRIVATE-TOKEN: ''$${varBase}PASSWORD
               EOF
-              curlOpts+=(--header @./private-token)
+              curlOpts="$curlOpts --header @./private-token"
             ''
         );
         netrcImpureEnvVars = [
diff --git a/pkgs/build-support/fetchurl/default.nix b/pkgs/build-support/fetchurl/default.nix
index 5d4f4e6dea15f..763bf5429cc13 100644
--- a/pkgs/build-support/fetchurl/default.nix
+++ b/pkgs/build-support/fetchurl/default.nix
@@ -339,7 +339,7 @@ lib.extendMkDerivation {
         else
           ''
             ${netrcPhase}
-            curlOpts+=(--netrc-file "$PWD/netrc")
+            curlOpts="$curlOpts --netrc-file $PWD/netrc"
           '';
 
       inherit meta;