diff --git a/lib/customisation.nix b/lib/customisation.nix
index 823395f04d4..d942f54ee79 100644
--- a/lib/customisation.nix
+++ b/lib/customisation.nix
@@ -155,12 +155,6 @@ rec {
       outPath = assert condition; drv.outPath;
     };
 
-  /* Add attributes to each output of a derivation without changing
-     the derivation itself. */
-  addPassthru =
-    lib.warn "`addPassthru drv passthru` is deprecated, replace with `extendDerivation true passthru drv`"
-      (drv: passthru: extendDerivation true passthru drv);
-
   /* Strip a derivation of all non-essential attributes, returning
      only those needed by hydra-eval-jobs. Also strictly evaluate the
      result to ensure that there are no thunks kept alive to prevent
diff --git a/lib/default.nix b/lib/default.nix
index 77cfa712557..a25a23299b3 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -88,7 +88,7 @@ let
     inherit (stringsWithDeps) textClosureList textClosureMap
       noDepEntry fullDepEntry packEntry stringAfter;
     inherit (customisation) overrideDerivation makeOverridable
-      callPackageWith callPackagesWith extendDerivation addPassthru
+      callPackageWith callPackagesWith extendDerivation
       hydraJob makeScope;
     inherit (meta) addMetaAttrs dontDistribute setName updateName
       appendToName mapDerivationAttrset lowPrio lowPrioSet hiPrio
diff --git a/nixos/doc/manual/release-notes/rl-1803.xml b/nixos/doc/manual/release-notes/rl-1803.xml
index 9f80dcc2934..ca34d798a35 100644
--- a/nixos/doc/manual/release-notes/rl-1803.xml
+++ b/nixos/doc/manual/release-notes/rl-1803.xml
@@ -181,7 +181,7 @@ following incompatible changes:</para>
   </listitem>
   <listitem>
     <para>
-      <literal>lib.addPassthru drv passthru</literal> is removed.  Use <literal>lib.extendDerivation true passthru drv</literal> instead.  <emphasis role="strong">TODO: actually remove it before branching 18.03 off.</emphasis>
+      <literal>lib.addPassthru drv passthru</literal> is removed.  Use <literal>lib.extendDerivation true passthru drv</literal> instead.
     </para>
   </listitem>
   <listitem>