diff --git a/overrides.nix b/overrides.nix
index 671d612..7a0caa4 100644
--- a/overrides.nix
+++ b/overrides.nix
@@ -35,95 +35,58 @@ let
           )
           filteredNames
         );
-  removeDependencies = names: deps:
-    with builtins; with pkgs.lib;
-      filter
-      (drv: all
-        (suf:
-          ! hasSuffix ("-" + suf)
-          (parseDrvName drv.name).name
-        )
-        names
-      )
-      deps;
 
-in skipOverrides {
+  combineCorrections = corrections: self: old:
+    builtins.foldl'
+    (updatedDerivation: correction: correction self updatedDerivation)
+    old
+    corrections;
 
-  "apipkg" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
+  addBuildInputs = names: self: old: {
+    buildInputs = old.buildInputs ++ builtins.map (name: self."${name}") names;
   };
 
-  "clickclick" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."six" self."flake8" ];
-  };
+in skipOverrides {
 
-  "connexion" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."flake8" ];
-  };
+  "apipkg" = addBuildInputs ["setuptools-scm"];
 
-  "execnet" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "clickclick" = addBuildInputs ["six" "flake8"];
 
-  "flake8-codeclimate" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "connexion" = addBuildInputs ["flake8"];
 
-  "flake8-logging-format" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."nose" ];
-  };
+  "execnet" = addBuildInputs ["setuptools-scm"];
 
-  "flake8-mutable" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."pytest-runner" ];
-  };
+  "flake8-codeclimate" = addBuildInputs ["setuptools-scm"];
 
-  "flake8-print" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."pytest-runner" ];
-  };
+  "flake8-logging-format" = addBuildInputs ["nose"];
 
-  "gevent-socketio" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."versiontools" ];
-  };
+  "flake8-mutable" = addBuildInputs ["pytest-runner"];
 
-  "jsonschema" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."vcversioner" ];
-  };
+  "flake8-print" = addBuildInputs ["pytest-runner"];
 
-  "PasteDeploy" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."pytest-runner" ];
-  };
+  "gevent-socketio" = addBuildInputs ["versiontools"];
 
-  "pluggy" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "jsonschema" = addBuildInputs ["vcversioner"];
 
-  "pygal" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."pytest-runner" ];
-  };
+  "PasteDeploy" = addBuildInputs ["pytest-runner"];
 
-  "pypiserver" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-git" ];
-  };
+  "pluggy" = addBuildInputs ["setuptools-scm"];
 
-  "pytest" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "py" = addBuildInputs ["setuptools-scm"];
 
-  "pytest-forked" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "pygal" = addBuildInputs ["pytest-runner"];
 
-  "pytest-xdist" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "pypiserver" = addBuildInputs ["setuptools-git"];
 
-  "python-dateutil" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "pytest" = addBuildInputs ["setuptools-scm"];
 
-  "requestsexceptions" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."pbr" ];
-  };
+  "pytest-forked" = addBuildInputs ["setuptools-scm"];
+
+  "pytest-xdist" = addBuildInputs ["setuptools-scm"];
+
+  "python-dateutil" = addBuildInputs ["setuptools-scm"];
+
+  "requestsexceptions" = addBuildInputs ["pbr"];
 
   "scipy" = self: old: {
      prePatch = ''
@@ -163,8 +126,6 @@ in skipOverrides {
       };
   };
 
-  "tox" = self: old: {
-    buildInputs = old.buildInputs ++ [ self."setuptools-scm" ];
-  };
+  "tox" = addBuildInputs ["setuptools-scm"];
 
 }
diff --git a/pytest/overrides.nix b/pytest/overrides.nix
index 78c8a0b..9569762 100644
--- a/pytest/overrides.nix
+++ b/pytest/overrides.nix
@@ -2,13 +2,6 @@
 
 self: super: {
 
-  "attrs" = python.overrideDerivation super."attrs" (old: {
-    propagatedBuildInputs =
-      builtins.filter
-        (x: (builtins.parseDrvName x.name).name != "${python.__old.python.libPrefix}-${python.__old.python.libPrefix}-pytest")
-        old.propagatedBuildInputs;
-  });
-
   "parse-type" = python.overrideDerivation super."parse-type" (old: {
     patchPhase = ''
       sed -i \