diff --git a/pkgs/os-specific/linux/lttng-modules/default.nix b/pkgs/os-specific/linux/lttng-modules/default.nix
index ee80b7632ba1e9..7495deb231d21b 100644
--- a/pkgs/os-specific/linux/lttng-modules/default.nix
+++ b/pkgs/os-specific/linux/lttng-modules/default.nix
@@ -23,7 +23,9 @@ stdenv.mkDerivation rec {
   meta = with stdenv.lib; {
     description = "Linux kernel modules for LTTng tracing";
     homepage = http://lttng.org/;
-    license = with licenses; [ lgpl21 gpl2 mit ];
+    # TODO: Add "mit" to the license list once the license attr set vs string
+    # decision has been made. (Having "mit" there breaks hydra evaluation.)
+    license = with licenses; [ lgpl21 gpl2 ];
     platforms = platforms.linux;
     maintainers = [ maintainers.bjornfor ];
   };