diff --git a/lib/load-cabal-plan.nix b/lib/load-cabal-plan.nix
index 14ba6db55a..adf3a6898d 100644
--- a/lib/load-cabal-plan.nix
+++ b/lib/load-cabal-plan.nix
@@ -47,7 +47,15 @@ let
               name = pkgs.lib.removePrefix "${prefix}:" n;
               value = (if cabal2nixComponents == null then {} else cabal2nixComponents.${collectionName}.${name}) // {
                 buildable = true;
-              } // lookupDependencies hsPkgs c.depends c.exe-depends;
+              } // lookupDependencies hsPkgs (
+                    c.depends
+                    # If plan.json uses a single unit for this package (build-type: Custom),
+                    # then it will leave the package itself out of `c.depends` for the
+                    # components of the package.
+                    # Haskell.nix builds the components separately so we need
+                    # to add the `library` component as a dependency.
+                    ++ pkgs.lib.optional (p ? components && p.components ? lib) p.id
+                  ) c.exe-depends;
             in { inherit name value; }
           )) components));
     in
diff --git a/test/setup-deps/pkg/src/Pkg.hs b/test/setup-deps/pkg/src/Pkg.hs
new file mode 100644
index 0000000000..fc1111aa2e
--- /dev/null
+++ b/test/setup-deps/pkg/src/Pkg.hs
@@ -0,0 +1,4 @@
+module Pkg where
+
+foo :: Int
+foo = 1
diff --git a/test/setup-deps/pkg/src/conduit-test.hs b/test/setup-deps/pkg/src/conduit-test.hs
deleted file mode 100644
index 696025f9fc..0000000000
--- a/test/setup-deps/pkg/src/conduit-test.hs
+++ /dev/null
@@ -1,5 +0,0 @@
-module Main where
-
-import Conduit
-
-main = return ()