diff --git a/pkgs/top-level/perl-packages.nix b/pkgs/top-level/perl-packages.nix
index cfab482a9b5..962a2b84c2f 100644
--- a/pkgs/top-level/perl-packages.nix
+++ b/pkgs/top-level/perl-packages.nix
@@ -12383,7 +12383,7 @@ let
     version = "1.20200211";
 
     src = fetchurl {
-      url = mirror://cpan/authors/id/C/CH/CHROMATIC/Modern-Perl-1.20200211.tar.gz;
+      url = "mirror://cpan/authors/id/C/CH/CHROMATIC/Modern-Perl-1.20200211.tar.gz";
       sha256 = "da1c83cee84fab9edb9e31d7f7abac43e1337b2e66015191ec4b6da59298c480";
     };
     meta = {