diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index f5c132a83..f3f6f01cc 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -305,7 +305,7 @@ public:
     GoalPtr makeDerivationGoal(const StorePath & drvPath, const StringSet & wantedOutputs, BuildMode buildMode = bmNormal);
     std::shared_ptr<DerivationGoal> makeBasicDerivationGoal(StorePath && drvPath,
         const BasicDerivation & drv, BuildMode buildMode = bmNormal);
-    GoalPtr makeSubstitutionGoal(const StorePath & storePath, RepairFlag repair = NoRepair);
+    GoalPtr makeSubstitutionGoal(const StorePath & storePath, RepairFlag repair = NoRepair, std::optional<std::string> ca = std::nullopt);
 
     /* Remove a dead goal. */
     void removeGoal(GoalPtr goal);
@@ -1195,7 +1195,7 @@ void DerivationGoal::haveDerivation()
        them. */
     if (settings.useSubstitutes && parsedDrv->substitutesAllowed())
         for (auto & i : invalidOutputs)
-            addWaitee(worker.makeSubstitutionGoal(i, buildMode == bmRepair ? Repair : NoRepair));
+            addWaitee(worker.makeSubstitutionGoal(i, buildMode == bmRepair ? Repair : NoRepair, getDerivationCA(*drv)));
 
     if (waitees.empty()) /* to prevent hang (no wake-up event) */
         outputsSubstituted();
@@ -4268,8 +4268,11 @@ private:
     typedef void (SubstitutionGoal::*GoalState)();
     GoalState state;
 
+    /* Content address for recomputing store path */
+    std::optional<std::string> ca;
+
 public:
-    SubstitutionGoal(StorePath && storePath, Worker & worker, RepairFlag repair = NoRepair);
+    SubstitutionGoal(StorePath && storePath, Worker & worker, RepairFlag repair = NoRepair, std::optional<std::string> ca = std::nullopt);
     ~SubstitutionGoal();
 
     void timedOut() override { abort(); };
@@ -4304,10 +4307,11 @@ public:
 };
 
 
-SubstitutionGoal::SubstitutionGoal(StorePath && storePath, Worker & worker, RepairFlag repair)
+SubstitutionGoal::SubstitutionGoal(StorePath && storePath, Worker & worker, RepairFlag repair, std::optional<std::string> ca)
     : Goal(worker)
     , storePath(std::move(storePath))
     , repair(repair)
+    , ca(ca)
 {
     state = &SubstitutionGoal::init;
     name = fmt("substitution of '%s'", worker.store.printStorePath(this->storePath));
@@ -4382,14 +4386,13 @@ void SubstitutionGoal::tryNext()
     sub = subs.front();
     subs.pop_front();
 
-    if (sub->storeDir != worker.store.storeDir) {
-        tryNext();
-        return;
-    }
+    auto subPath = storePath.clone();
+    if (ca && (hasPrefix(*ca, "fixed:") || hasPrefix(*ca, "text:")))
+        subPath = sub->makeFixedOutputPathFromCA(storePath.name(), *ca);
 
     try {
         // FIXME: make async
-        info = sub->queryPathInfo(storePath);
+        info = sub->queryPathInfo(subPath);
     } catch (InvalidPath &) {
         tryNext();
         return;
@@ -4408,6 +4411,19 @@ void SubstitutionGoal::tryNext()
         throw;
     }
 
+    if (info->path != storePath) {
+        if (info->isContentAddressed(*sub)) {
+            auto info2 = std::const_pointer_cast<ValidPathInfo>(std::shared_ptr<const ValidPathInfo>(info));
+            info2->path = storePath.clone();
+            info = info2;
+        } else {
+            printError("asked '%s' for '%s' but got '%s'",
+                sub->getUri(), worker.store.printStorePath(storePath), sub->printStorePath(info->path));
+            tryNext();
+            return;
+        }
+    }
+
     /* Update the total expected download size. */
     auto narInfo = std::dynamic_pointer_cast<const NarInfo>(info);
 
@@ -4493,8 +4509,12 @@ void SubstitutionGoal::tryToRun()
             Activity act(*logger, actSubstitute, Logger::Fields{worker.store.printStorePath(storePath), sub->getUri()});
             PushActivity pact(act.id);
 
+            auto subPath = storePath.clone();
+            if (ca && (hasPrefix(*ca, "fixed:") || hasPrefix(*ca, "text:")))
+                subPath = sub->makeFixedOutputPathFromCA(storePath.name(), *ca);
+
             copyStorePath(ref<Store>(sub), ref<Store>(worker.store.shared_from_this()),
-                storePath, repair, sub->isTrusted ? NoCheckSigs : CheckSigs);
+                subPath, repair, sub->isTrusted ? NoCheckSigs : CheckSigs);
 
             promise.set_value();
         } catch (...) {
@@ -4628,11 +4648,11 @@ std::shared_ptr<DerivationGoal> Worker::makeBasicDerivationGoal(StorePath && drv
 }
 
 
-GoalPtr Worker::makeSubstitutionGoal(const StorePath & path, RepairFlag repair)
+GoalPtr Worker::makeSubstitutionGoal(const StorePath & path, RepairFlag repair, std::optional<std::string> ca)
 {
     GoalPtr goal = substitutionGoals[path.clone()].lock(); // FIXME
     if (!goal) {
-        goal = std::make_shared<SubstitutionGoal>(path.clone(), *this, repair);
+        goal = std::make_shared<SubstitutionGoal>(path.clone(), *this, repair, ca);
         substitutionGoals.insert_or_assign(path.clone(), goal);
         wakeUp(goal);
     }
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 1b0a055d3..109e9e473 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -108,12 +108,12 @@ void Store::computeFSClosure(const StorePath & startPath,
 }
 
 
-static std::optional<std::string> getDerivationCA(ref<Derivation> drv)
+std::optional<std::string> getDerivationCA(const BasicDerivation & drv)
 {
-    auto outputHashMode = drv->env.find("outputHashMode");
-    auto outputHashAlgo = drv->env.find("outputHashAlgo");
-    auto outputHash = drv->env.find("outputHash");
-    if (outputHashMode != drv->env.end() && outputHashAlgo != drv->env.end() && outputHash != drv->env.end()) {
+    auto outputHashMode = drv.env.find("outputHashMode");
+    auto outputHashAlgo = drv.env.find("outputHashAlgo");
+    auto outputHash = drv.env.find("outputHash");
+    if (outputHashMode != drv.env.end() && outputHashAlgo != drv.env.end() && outputHash != drv.env.end()) {
         auto ht = parseHashType(outputHashAlgo->second);
         auto h = Hash(outputHash->second, ht);
         FileIngestionMethod ingestionMethod;
@@ -182,7 +182,7 @@ void Store::queryMissing(const std::vector<StorePathWithOutputs> & targets,
         paths.insert(outPath.clone());
 
         std::map<std::string, std::string> pathsCA = {};
-        if (auto ca = getDerivationCA(drv))
+        if (auto ca = getDerivationCA(*drv))
             pathsCA.insert({outPathS, *ca});
         querySubstitutablePathInfos(paths, infos, pathsCA);
 
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 9412785b4..9918a36c6 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -855,4 +855,6 @@ std::string makeFixedOutputCA(FileIngestionMethod method, const Hash & hash);
 /* Split URI into protocol+hierarchy part and its parameter set. */
 std::pair<std::string, Store::Params> splitUriAndParams(const std::string & uri);
 
+std::optional<std::string> getDerivationCA(const BasicDerivation & drv);
+
 }
diff --git a/tests/fetchurl.sh b/tests/fetchurl.sh
index f4b86d251..aaa38f2ed 100644
--- a/tests/fetchurl.sh
+++ b/tests/fetchurl.sh
@@ -32,13 +32,13 @@ cmp $outPath fetchurl.sh
 # Test that we can substitute from a different store dir.
 clearStore
 
-other_store=file://$TEST_ROOT/other_store
+other_store=file://$TEST_ROOT/other_store?store=/fnord/store
 
 hash=$(nix hash-file --type sha256 --base16 ./fetchurl.sh)
 
 storePath=$(nix --store $other_store add-to-store --flat ./fetchurl.sh)
 
-outPath=$(nix-build '<nix/fetchurl.nix>' --argstr url file:///no-such-dir/fetchurl.sh --argstr sha256 $hash --no-out-link --substituters $other_store)
+outPath=$(nix-build -vvvvv '<nix/fetchurl.nix>' --argstr url file:///no-such-dir/fetchurl.sh --argstr sha256 $hash --no-out-link --substituters $other_store)
 
 # Test hashed mirrors with an SRI hash.
 nix-build '<nix/fetchurl.nix>' --argstr url file:///no-such-dir/fetchurl.sh --argstr hash $(nix to-sri --type sha256 $hash) \