diff --git a/pkgs/development/python-modules/actdiag/default.nix b/pkgs/development/python-modules/actdiag/default.nix
index 2172aa1165a6..27a9a455c47f 100644
--- a/pkgs/development/python-modules/actdiag/default.nix
+++ b/pkgs/development/python-modules/actdiag/default.nix
@@ -1,5 +1,5 @@
-{ stdenv, buildPythonPackage, fetchPypi
-, pep8, nose, unittest2, docutils, blockdiag  }:
+{ stdenv, buildPythonPackage, fetchPypi, fetchpatch
+, pep8, nose, unittest2, docutils, blockdiag, reportlab }:
 
 buildPythonPackage rec {
   pname = "actdiag";
@@ -10,13 +10,17 @@ buildPythonPackage rec {
     sha256 = "983071777d9941093aaef3be1f67c198a8ac8d2bba264cdd1f337ca415ab46af";
   };
 
+  patches = fetchpatch {
+    name = "drop_test_pep8.py.patch";
+    url = https://bitbucket.org/blockdiag/actdiag/commits/c1f2ed5947a1e93291f5860e4e30cee098bd635d/raw;
+    sha256 = "1zxzwb0fvwlc8xgs45fx65341sjhb3h6l2p6rdj6i127vg1hsxb4";
+  };
+
   buildInputs = [ pep8 nose unittest2 docutils ];
 
   propagatedBuildInputs = [ blockdiag ];
 
-  # One test fails:
-  #   UnicodeEncodeError: 'ascii' codec can't encode character u'\u3042' in position 0: ordinal not in range(128)
-  doCheck = false;
+  checkInputs = [ reportlab ];
 
   meta = with stdenv.lib; {
     description = "Generate activity-diagram image from spec-text file (similar to Graphviz)";