diff --git a/pkgs/tools/networking/dd-agent/6.nix b/pkgs/tools/networking/dd-agent/6.nix
index be5f016c187b..56a71595cea7 100644
--- a/pkgs/tools/networking/dd-agent/6.nix
+++ b/pkgs/tools/networking/dd-agent/6.nix
@@ -1,8 +1,6 @@
 { stdenv, fetchFromGitHub, buildGoPackage, makeWrapper, pythonPackages, pkgconfig }:
 
 let
-  inherit (pythonPackages) python;
-
   # keep this in sync with github.com/DataDog/agent-payload dependency
   payloadVersion = "4.7";
 
@@ -27,6 +25,9 @@ in buildGoPackage rec {
   goDeps = ./deps.nix;
   goPackagePath = "github.com/${owner}/${repo}";
 
+  # Explicitly set this here to allow it to be overridden.
+  python = pythonPackages.python;
+
   nativeBuildInputs = [ pkgconfig makeWrapper ];
   PKG_CONFIG_PATH = "${python}/lib/pkgconfig";
 
diff --git a/pkgs/tools/networking/dd-agent/integrations-core.nix b/pkgs/tools/networking/dd-agent/integrations-core.nix
index 2efc82473690..9212209e775b 100644
--- a/pkgs/tools/networking/dd-agent/integrations-core.nix
+++ b/pkgs/tools/networking/dd-agent/integrations-core.nix
@@ -1,7 +1,39 @@
-{ pkgs
-, python
-, overrides ? (self: super: {})
-}:
+# The declarations in this file build the Datadog agent's core
+# integrations. These integrations are tracked in a separate
+# repository[1] outside of the agent's primary repository and provide
+# checks for various kinds of services.
+#
+# Not all services are relevant for all users, however. As some of
+# them depend on various tools and Python packages it is nonsensical
+# to build *all* integrations by default.
+#
+# A set of default integrations is defined and built either way.
+# Additional integrations can be specified by overriding
+# `extraIntegrations` in datadog-integrations-core.
+#
+# In practice the syntax for using this with additional integrations
+# is not the most beautiful, but it works. For example to use
+# datadog-agent from the top-level with the `ntp`-integration
+# included, one could say:
+#
+# let
+#   integrationsWithNtp = datadog-integrations-core {
+#     # Extra integrations map from the integration name (as in the
+#     # integrations-core repository) to a function that receives the
+#     # Python package set and returns the required dependencies.g
+#     ntp = (ps: [ ps.ntplib ]);
+#   };
+#
+# in ddAgentWithNtp = datadog-agent.overrideAttrs(_ : {
+#   python = integrationsWithNtp.python;
+# });
+#
+# The NixOS module 'datadog-agent' provides a simplified interface to
+# this. Please see the module itself for more information.
+#
+# [1]: https://github.com/DataDog/integrations-core
+
+{ pkgs, python, extraIntegrations ? {} }:
 
 with pkgs.lib;
 
@@ -14,6 +46,7 @@ let
   };
   version = "git-2018-05-27";
 
+  # Build helper to build a single datadog integration package.
   buildIntegration = { pname, ... }@args: python.pkgs.buildPythonPackage (args // {
     inherit src version;
     name = "datadog-integration-${pname}-${version}";
@@ -27,40 +60,32 @@ let
     doCheck = false;
   });
 
-  packages = (self: {
-    python = python.withPackages (ps: with self; [ disk network postgres nginx mongo ]);
+  # Base package depended on by all other integrations.
+  datadog_checks_base = buildIntegration {
+    pname = "checks-base";
+    sourceRoot = "datadog_checks_base";
+    propagatedBuildInputs = with python.pkgs; [
+      requests protobuf prometheus_client uuid simplejson uptime
+    ];
+  };
 
-    datadog_checks_base = buildIntegration {
-      pname = "checks-base";
-      sourceRoot = "datadog_checks_base";
-      propagatedBuildInputs = with self; with python.pkgs; [ requests protobuf prometheus_client uuid simplejson uptime ];
-    };
+  # Default integrations that should be built:
+  defaultIntegrations = {
+    disk     = (ps: [ ps.psutil ]);
+    mongo    = (ps: [ ps.pymongo ]);
+    network  = (ps: [ ps.psutil ]);
+    nginx    = (ps: []);
+    postgres = (ps: with ps; [ pg8000 psycopg2 ]);
+  };
 
-    disk = buildIntegration {
-      pname = "disk";
-      propagatedBuildInputs = with self; with python.pkgs; [ datadog_checks_base psutil ];
-    };
+  # All integrations (default + extra):
+  integrations = defaultIntegrations // extraIntegrations;
+  builtIntegrations = mapAttrs (pname: fdeps: buildIntegration {
+    inherit pname;
+    propagatedBuildInputs = (fdeps python.pkgs) ++ [ datadog_checks_base ];
+  }) integrations;
 
-    network = buildIntegration {
-      pname = "network";
-      propagatedBuildInputs = with self; with python.pkgs; [ datadog_checks_base psutil ];
-    };
-
-    postgres = buildIntegration {
-      pname = "postgres";
-      propagatedBuildInputs = with self; with python.pkgs; [ datadog_checks_base pg8000 psycopg2 ];
-    };
-
-    nginx = buildIntegration {
-      pname = "nginx";
-      propagatedBuildInputs = with self; with python.pkgs; [ datadog_checks_base ];
-    };
-
-    mongo = buildIntegration {
-      pname = "mongo";
-      propagatedBuildInputs = with self; with python.pkgs; [ datadog_checks_base pymongo ];
-    };
-
-  });
-
-in fix' (extends overrides packages)
+in builtIntegrations // {
+  inherit datadog_checks_base;
+  python = python.withPackages (_: (attrValues builtIntegrations));
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 323a5daab3cc..3d50a280ac5e 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -15674,10 +15674,11 @@ with pkgs;
 
   dd-agent = callPackage ../tools/networking/dd-agent/5.nix { };
   datadog-agent = callPackage ../tools/networking/dd-agent/6.nix {
-    pythonPackages = datadog-integrations-core;
+    pythonPackages = datadog-integrations-core {};
   };
-  datadog-integrations-core = callPackage ../tools/networking/dd-agent/integrations-core.nix {
+  datadog-integrations-core = extras: callPackage ../tools/networking/dd-agent/integrations-core.nix {
     python = python27;
+    extraIntegrations = extras;
   };
 
   ddgr = callPackage ../applications/misc/ddgr { };