diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index b5d8d1a1c..fa8bc58ac 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -426,7 +426,9 @@ Derivation parseDerivation(
         if (*versionS == "xp-dyn-drv"sv) {
             // Only version we have so far
             version = DerivationATermVersion::DynamicDerivations;
-            xpSettings.require(Xp::DynamicDerivations, fmt("derivation '%s', ATerm format version 'xp-dyn-drv'", name));
+            xpSettings.require(Xp::DynamicDerivations, [&] {
+                return fmt("derivation '%s', ATerm format version 'xp-dyn-drv'", name);
+            });
         } else {
             throw FormatError("Unknown derivation ATerm format version '%s'", *versionS);
         }
@@ -1454,7 +1456,8 @@ Derivation Derivation::fromJSON(const nlohmann::json & _json, const Experimental
             node.value = getStringSet(valueAt(json, "outputs"));
             auto drvs = getObject(valueAt(json, "dynamicOutputs"));
             for (auto & [outputId, childNode] : drvs) {
-                xpSettings.require(Xp::DynamicDerivations, fmt("dynamic output '%s' in JSON", outputId));
+                xpSettings.require(
+                    Xp::DynamicDerivations, [&] { return fmt("dynamic output '%s' in JSON", outputId); });
                 node.childMap[outputId] = doInput(childNode);
             }
             return node;
diff --git a/src/libstore/derived-path.cc b/src/libstore/derived-path.cc
index 34e591666..8d606cb41 100644
--- a/src/libstore/derived-path.cc
+++ b/src/libstore/derived-path.cc
@@ -86,9 +86,9 @@ void drvRequireExperiment(const SingleDerivedPath & drv, const ExperimentalFeatu
                 // plain drv path; no experimental features required.
             },
             [&](const SingleDerivedPath::Built & b) {
-                xpSettings.require(
-                    Xp::DynamicDerivations,
-                    fmt("building output '%s' of '%s'", b.output, b.drvPath->getBaseStorePath().to_string()));
+                xpSettings.require(Xp::DynamicDerivations, [&] {
+                    return fmt("building output '%s' of '%s'", b.output, b.drvPath->getBaseStorePath().to_string());
+                });
             },
         },
         drv.raw());
diff --git a/src/libstore/downstream-placeholder.cc b/src/libstore/downstream-placeholder.cc
index 30044501b..780717a62 100644
--- a/src/libstore/downstream-placeholder.cc
+++ b/src/libstore/downstream-placeholder.cc
@@ -24,7 +24,8 @@ DownstreamPlaceholder DownstreamPlaceholder::unknownDerivation(
     OutputNameView outputName,
     const ExperimentalFeatureSettings & xpSettings)
 {
-    xpSettings.require(Xp::DynamicDerivations, fmt("placeholder for unknown derivation output '%s'", outputName));
+    xpSettings.require(
+        Xp::DynamicDerivations, [&] { return fmt("placeholder for unknown derivation output '%s'", outputName); });
     auto compressed = compressHash(placeholder.hash, 20);
     auto clearText =
         "nix-computed-output:" + compressed.to_string(HashFormat::Nix32, false) + ":" + std::string{outputName};
diff --git a/src/libutil/include/nix/util/configuration.hh b/src/libutil/include/nix/util/configuration.hh
index c8d7b7f24..541febdb5 100644
--- a/src/libutil/include/nix/util/configuration.hh
+++ b/src/libutil/include/nix/util/configuration.hh
@@ -465,6 +465,19 @@ struct ExperimentalFeatureSettings : Config
      */
     void require(const ExperimentalFeature &, std::string reason = "") const;
 
+    /**
+     * Require an experimental feature be enabled, throwing an error if it is
+     * not. The reason is lazily evaluated only if the feature is disabled.
+     */
+    template<typename GetReason>
+        requires std::invocable<GetReason> && std::convertible_to<std::invoke_result_t<GetReason>, std::string>
+    void require(const ExperimentalFeature & feature, GetReason && getReason) const
+    {
+        if (isEnabled(feature))
+            return;
+        require(feature, getReason());
+    }
+
     /**
      * `std::nullopt` pointer means no feature, which means there is nothing that could be
      * disabled, and so the function returns true in that case.