diff --git a/pkgs/tools/graphics/gnuplot/default.nix b/pkgs/tools/graphics/gnuplot/default.nix
index d50adaa387f..f2be9fafc60 100644
--- a/pkgs/tools/graphics/gnuplot/default.nix
+++ b/pkgs/tools/graphics/gnuplot/default.nix
@@ -61,6 +61,15 @@ stdenv.mkDerivation rec {
     homepage = http://www.gnuplot.info/;
     description = "A portable command-line driven graphing utility for many platforms";
     platforms = platforms.linux ++ platforms.darwin;
+    license = {
+      # Essentially a BSD license with one modifaction:
+      # Permission to modify the software is granted, but not the right to
+      # distribute the complete modified source code.  Modifications are to
+      # be distributed as patches to the released version.  Permission to
+      # distribute binaries produced by compiling modified sources is granted,
+      # provided you: ...
+      url = https://sourceforge.net/p/gnuplot/gnuplot-main/ci/master/tree/Copyright;
+    };
     maintainers = with maintainers; [ lovek323 ];
   };
 }