diff --git a/pkgs/build-support/fetchgitlab/default.nix b/pkgs/build-support/fetchgitlab/default.nix
index 8a2b0ffa31d6b..7ac209654967d 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="$curlOpts --header @./private-token"
+              curlOpts+=(--header @./private-token)
             ''
         );
         netrcImpureEnvVars = [
diff --git a/pkgs/build-support/fetchurl/default.nix b/pkgs/build-support/fetchurl/default.nix
index 8d3283039f115..b573860829fe1 100644
--- a/pkgs/build-support/fetchurl/default.nix
+++ b/pkgs/build-support/fetchurl/default.nix
@@ -339,7 +339,7 @@ lib.extendMkDerivation {
         else
           ''
             ${netrcPhase}
-            curlOpts="$curlOpts --netrc-file $PWD/netrc"
+            curlOpts+=(--netrc-file "$PWD/netrc")
           '';
 
       inherit meta;