diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index e6b552b94..60495ae3e 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1086,10 +1086,9 @@ void LocalDerivationGoal::initEnv()
 
 void LocalDerivationGoal::writeStructuredAttrs()
 {
-    if (auto structAttrs = parsedDrv->generateStructuredAttrs(inputRewrites, worker.store, inputPaths)) {
-        auto value = structAttrs.value();
-        auto jsonSh = value.first;
-        auto json = value.second;
+    if (auto structAttrsJson = parsedDrv->prepareStructuredAttrs(inputRewrites, worker.store, inputPaths)) {
+        auto json = structAttrsJson.value();
+        auto jsonSh = parsedDrv->writeStructuredAttrsShell(json);
 
         writeFile(tmpDir + "/.attrs.sh", rewriteStrings(jsonSh, inputRewrites));
         chownToBuilder(tmpDir + "/.attrs.sh");
diff --git a/src/libstore/parsed-derivations.cc b/src/libstore/parsed-derivations.cc
index 029da8bd3..5675600c4 100644
--- a/src/libstore/parsed-derivations.cc
+++ b/src/libstore/parsed-derivations.cc
@@ -124,8 +124,7 @@ bool ParsedDerivation::substitutesAllowed() const
 }
 
 static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
-std::optional<StructuredAttrsWithShellRC> ParsedDerivation::generateStructuredAttrs(
-    std::optional<StringMap> inputRewrites, Store & store, const StorePathSet & inputPaths)
+std::optional<nlohmann::json> ParsedDerivation::prepareStructuredAttrs(std::optional<StringMap> inputRewrites, Store & store, const StorePathSet & inputPaths)
 {
     auto structuredAttrs = getStructuredAttrs();
     if (!structuredAttrs) return std::nullopt;
@@ -163,6 +162,11 @@ std::optional<StructuredAttrsWithShellRC> ParsedDerivation::generateStructuredAt
         }
     }
 
+    return json;
+}
+
+std::string ParsedDerivation::writeStructuredAttrsShell(nlohmann::json & json)
+{
     /* As a convenience to bash scripts, write a shell file that
        maps all attributes that are representable in bash -
        namely, strings, integers, nulls, Booleans, and arrays and
@@ -229,6 +233,6 @@ std::optional<StructuredAttrsWithShellRC> ParsedDerivation::generateStructuredAt
         }
     }
 
-    return std::make_pair(jsonSh, json);
+    return jsonSh;
 }
 }
diff --git a/src/libstore/parsed-derivations.hh b/src/libstore/parsed-derivations.hh
index 4b8b8c8ff..37af36630 100644
--- a/src/libstore/parsed-derivations.hh
+++ b/src/libstore/parsed-derivations.hh
@@ -39,7 +39,8 @@ public:
 
     bool substitutesAllowed() const;
 
-    std::optional<StructuredAttrsWithShellRC> generateStructuredAttrs(std::optional<StringMap> inputRewrites, Store & store, const StorePathSet & inputPaths);
+    std::optional<nlohmann::json> prepareStructuredAttrs(std::optional<StringMap> inputRewrites, Store & store, const StorePathSet & inputPaths);
+    std::string writeStructuredAttrsShell(nlohmann::json & json);
 };
 
 }
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 9bd7869f9..4e4f27458 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -444,13 +444,16 @@ static void main_nix_build(int argc, char * * argv)
                 drv
             );
 
-            if (auto structAttrs = parsedDrv.generateStructuredAttrs(std::nullopt, *store, inputs)) {
-                auto val = structAttrs.value();
-                structuredAttrsRC = val.first;
+            if (auto structAttrs = parsedDrv.prepareStructuredAttrs(std::nullopt, *store, inputs)) {
+                auto json = structAttrs.value();
+                structuredAttrsRC = parsedDrv.writeStructuredAttrsShell(json);
+
                 auto attrsJSON = (Path) tmpDir + "/.attrs.json";
-                writeFile(attrsJSON, val.second.dump());
+                writeFile(attrsJSON, json.dump());
+
                 auto attrsSH = (Path) tmpDir + "/.attrs.sh";
-                writeFile(attrsSH, val.first);
+                writeFile(attrsSH, structuredAttrsRC);
+
                 env["ATTRS_SH_FILE"] = attrsSH;
                 env["ATTRS_JSON_FILE"] = attrsJSON;
                 keepTmp = true;