diff --git a/lix/libstore/build/local-derivation-goal.cc b/lix/libstore/build/local-derivation-goal.cc
index ddf628077..940f430c6 100644
--- a/lix/libstore/build/local-derivation-goal.cc
+++ b/lix/libstore/build/local-derivation-goal.cc
@@ -2512,8 +2512,24 @@ void LocalDerivationGoal::checkOutputs(const std::map<std::string, ValidPathInfo
                         spec.insert(output->path);
                     else if (auto storePath = get(alreadyRegisteredOutputs, i))
                         spec.insert(*storePath);
-                    else
-                        throw BuildError("derivation contains an illegal reference specifier '%s'", i);
+                    else {
+                        std::string outputsListing = concatMapStringsSep(
+                            ", ",
+                            newlyBuiltOutputs,
+                            [](auto & o) { return o.first; }
+                        );
+                        if (!alreadyRegisteredOutputs.empty()) {
+                            outputsListing.append(outputsListing.empty() ? "" : ", ");
+                            outputsListing.append(concatMapStringsSep(
+                                ", ",
+                                alreadyRegisteredOutputs,
+                                [](auto & o) { return o.first; })
+                            );
+                        }
+                        throw BuildError("derivation '%s' output check for '%s' contains an illegal reference specifier '%s',"
+                            " expected store path or output name (one of [%s])",
+                            worker.store.printStorePath(drvPath), outputName, i, outputsListing);
+                    }
                 }
 
                 auto used = recursive
diff --git a/lix/libutil/strings.hh b/lix/libutil/strings.hh
index 2f865c379..67238824a 100644
--- a/lix/libutil/strings.hh
+++ b/lix/libutil/strings.hh
@@ -5,6 +5,7 @@
 #include "lix/libutil/types.hh"
 
 #include <vector>
+#include <boost/container/small_vector.hpp>
 
 namespace nix {
 
@@ -34,7 +35,6 @@ MakeError(FormatError, Error);
  */
 template<class C> C tokenizeString(std::string_view s, std::string_view separators = " \t\n\r");
 
-
 /**
  * Concatenate the given strings with a separator between the
  * elements.
@@ -63,6 +63,22 @@ auto concatStrings(Parts && ... parts)
 }
 
 
+/**
+ * Apply a function to the `iterable`'s items and concat them with `separator`.
+ */
+template<class C, class F>
+std::string concatMapStringsSep(std::string_view separator, const C & iterable, F fn)
+{
+    boost::container::small_vector<std::string, 64> strings;
+    strings.reserve(iterable.size());
+    for (const auto & elem : iterable) {
+        strings.push_back(fn(elem));
+    }
+    return concatStringsSep(separator, strings);
+}
+
+
+
 /**
  * Add quotes around a collection of strings.
  */
diff --git a/tests/functional/check-refs.nix b/tests/functional/check-refs.nix
index 89690e456..1a900830e 100644
--- a/tests/functional/check-refs.nix
+++ b/tests/functional/check-refs.nix
@@ -74,4 +74,10 @@ rec {
     buildCommand = ''echo ${dep} > "''${outputs[out]}"'';
   };
 
+  test12 = makeTest 12 {
+    builder = builtins.toFile "builder.sh" "mkdir $out $lib";
+    outputs = ["out" "lib"];
+    disallowedReferences = ["dev"];
+  };
+
 }
diff --git a/tests/functional/check-refs.sh b/tests/functional/check-refs.sh
index 3b587d1e5..d4a5aa29f 100644
--- a/tests/functional/check-refs.sh
+++ b/tests/functional/check-refs.sh
@@ -51,3 +51,7 @@ if isDaemonNewer 2.12pre20230103; then
     test11=$(nix-build -o $RESULT check-refs.nix -A test11)
     [[ -z $(nix-store -q --references "$test11") ]]
 fi
+
+# test12 should fail (syntactically invalid).
+expectStderr 1 nix-build -vvv -o "$RESULT" check-refs.nix -A test12 >"$TEST_ROOT/test12.stderr"
+grepQuiet -F "output check for 'lib' contains an illegal reference specifier 'dev', expected store path or output name (one of [lib, out])" < "$TEST_ROOT/test12.stderr"
diff --git a/tests/unit/libutil/tests.cc b/tests/unit/libutil/tests.cc
index 1349be71f..00fcf8269 100644
--- a/tests/unit/libutil/tests.cc
+++ b/tests/unit/libutil/tests.cc
@@ -667,4 +667,43 @@ namespace nix {
         ASSERT_EQ(filterANSIEscapes("f𐍈𐍈bär", true, 4), "f𐍈𐍈b");
     }
 
+    /* ----------------------------------------------------------------------------
+     * concatMapStringsSep
+     * --------------------------------------------------------------------------*/
+    TEST(concatMapStringsSep, empty)
+    {
+        Strings strings;
+
+        ASSERT_EQ(concatMapStringsSep(",", strings, [](const std::string & s) { return s; }), "");
+    }
+
+    TEST(concatMapStringsSep, justOne)
+    {
+        Strings strings;
+        strings.push_back("this");
+
+        ASSERT_EQ(concatMapStringsSep(",", strings, [](const std::string & s) { return s; }), "this");
+    }
+
+    TEST(concatMapStringsSep, two)
+    {
+        Strings strings;
+        strings.push_back("this");
+        strings.push_back("that");
+
+        ASSERT_EQ(concatMapStringsSep(",", strings, [](const std::string & s) { return s; }), "this,that");
+    }
+
+    TEST(concatMapStringsSep, map)
+    {
+        std::map<std::string, std::string> strings;
+        strings["this"] = "that";
+        strings["1"] = "one";
+
+        ASSERT_EQ(
+            concatMapStringsSep(
+                ", ", strings, [](const std::pair<std::string, std::string> & s) { return s.first + " -> " + s.second; }),
+            "1 -> one, this -> that");
+    }
+
 }