1 files changed, 1 insertions, 1 deletions
diff --git a/nixpkgs/pkgs/applications/science/logic/prooftree/default.nix b/nixpkgs/pkgs/applications/science/logic/prooftree/default.nix
index d4feb5c9e285..98313e48cb27 100644
--- a/nixpkgs/pkgs/applications/science/logic/prooftree/default.nix
+++ b/nixpkgs/pkgs/applications/science/logic/prooftree/default.nix
@@ -35,7 +35,7 @@ stdenv.mkDerivation rec {
       below the tree (on single click) or in a separate window (on double or
       shift-click).
     '';
-    homepage = http://askra.de/software/prooftree;
+    homepage = "http://askra.de/software/prooftree";
     platforms = platforms.unix;
     maintainers = [ maintainers.jwiegley ];
     license = licenses.gpl3;